華為OJ題解（中級）
阿新 • • 發佈：2019-02-07
密碼驗證合格程式
import java.util.Scanner; public class Main { //子串出現次數(避免交叉) private static int countOf(String str,String subStr){ if(str.indexOf(subStr)==-1){ return 0; }else{ int indexOf=str.indexOf(subStr); return 1+countOf(str.substring(indexOf+subStr.length()),subStr); } } //判定所以子串(長度大於2)是否有重複 private static boolean isDuplicate(String str){ if(str.length()<=2) return false; for(int i=0;i<=str.length()-3;i++){ for(int j=i+3;j<=str.length();j++){ if(j-i>str.length()/2)break;//長度超過一半的子串忽略 if(countOf(str,str.substring(i,j))>=2){ return true; } } } return false; } //統計字元種數 private static int categoryNum(String str){ int number=0,bigger=0,little=0,other=0;//統計字元 for(int i=0;i<str.length();i++){ char c=str.charAt(i); if('0'<=c&&c<='9'){ number=1; }else{ if('A'<=c&&c<='Z'){ bigger=1; }else{ if('a'<=c&&c<='z'){ little=1; }else{ other=1; } } } } return number+bigger+little+other; } public static void main(String[] args){ Scanner in = new Scanner(System.in); while(in.hasNext()){ String s=in.next(); if(s.length()>8&&categoryNum(s)>=3&&!isDuplicate(s)){ System.out.println("OK"); }else{ System.out.println("NG"); } } } }
汽水瓶
import java.util.Scanner;
public class Main {
public static void main(String[] args){
Scanner in = new Scanner(System.in);
while(in.hasNext()){
int num=in.nextInt();
if(num==0)return;
System.out.println(num/2);
}
}
}刪除字串中出現次數最少的字元
import java.util.Scanner; public class Main { public static void main(String[] args){ Scanner in = new Scanner(System.in); String s=in.next(); int[] counts=new int[128]; for(int i=0;i<s.length();i++){//統計次數 counts[s.charAt(i)]++; } int min=Integer.MAX_VALUE; for(int i=0;i<128;i++){//尋找最小次數 if(counts[i]!=0){ min=Math.min(min, counts[i]); } } StringBuilder builder=new StringBuilder(); for(int i=0;i<s.length();i++){//計算結果 if(counts[s.charAt(i)]!=min){ builder.append(s.charAt(i)); } } System.out.println(builder.toString()); } }
字串排序
import java.util.Scanner; public class Main { public static void main(String[] args){ Scanner in = new Scanner(System.in); String s=in.nextLine(); StringBuilder builder=new StringBuilder(); for(int i=0;i<s.length();i++){ char c=s.charAt(i); if(('a'<=c&&c<='z')||('A'<=c&&c<='Z')){ builder.append(c); } } char[] cs=builder.toString().toCharArray();//記錄所有字元 for(int i=cs.length-1;i>0;i--){//冒泡，穩定（可以採用歸併排序） for(int j=0;j<i;j++){ if(Character.toUpperCase(cs[j])>Character.toUpperCase(cs[j+1])){ char t=cs[j];cs[j]=cs[j+1];cs[j+1]=t; } } } builder.setLength(0);//清空builder int index=0; for(int i=0;i<s.length();i++){//綜合得到結果 char c=s.charAt(i); if(('a'<=c&&c<='z')||('A'<=c&&c<='Z')){ builder.append(cs[index++]); }else{ builder.append(c); } } System.out.println(builder.toString()); } }
查詢兄弟單詞
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Scanner;
public class Main {
//將字元轉換成排序後的標準形式
private static boolean isBrother(String a,String b){
if(a.length()!=b.length()) return false;
int[] countA=new int[26];
int[] countB=new int[26];
for(int i=0;i<a.length();i++){
countA[a.charAt(i)-'a']++;
}
for(int i=0;i<b.length();i++){
countB[b.charAt(i)-'a']++;
}
for(int i=0;i<26;i++){
if(countA[i]!=countB[i])return false;
}
return true;
}
public static void main(String[] args){
Scanner in = new Scanner(System.in);
ArrayList<String> words=new ArrayList<String>();
int n=in.nextInt();
for(int i=0;i<n;i++){
words.add(in.next());
}
String find=in.next();
int index=in.nextInt();
ArrayList<String> brothers=new ArrayList<String>();
HashMap<String,Boolean> findedBrother=new HashMap<String,Boolean>();//過濾重複兄弟
for(String s:words){
if(isBrother(s,find)&&!s.equals(find)&&!findedBrother.containsKey(s)){
brothers.add(s);
findedBrother.put(s, true);
}
}
Collections.sort(brothers);//對兄弟字典排序
System.out.println(brothers.size());
System.out.println(brothers.get(index-1));
}
}[中級]單詞倒排
import java.util.ArrayList;
import java.util.Scanner;
public class Main {
private static boolean isCharacter(char c){
return ('a'<=c&&c<='z')||('A'<=c&&c<='Z')?true:false;
}
public static void main(String[] args){
Scanner in = new Scanner(System.in);
ArrayList<String> words=new ArrayList<String>();
StringBuilder candidate=new StringBuilder();
String s=in.nextLine();
for(int i=0;i<s.length();i++){
char c=s.charAt(i);
if(isCharacter(c)){//字母加入
candidate.append(c);
}else{//遇到非字母
if(candidate.length()!=0){//如果有單詞則新增
words.add(candidate.toString());
candidate.setLength(0);//重置
}
}
}
if(candidate.length()!=0){//末尾處理
words.add(candidate.toString());
candidate.setLength(0);
}
if(words.size()==0)return;
for(int i=words.size()-1;i>=1;i--){
System.out.print(words.get(i)+" ");
}
System.out.print(words.get(0));
}
}整數與IP地址間的轉換
import java.util.Scanner;
public class Main {
private static int ipToInt(String ip){
String[] values=ip.split("\\.");
int one=Integer.parseInt(values[0]);
int two=Integer.parseInt(values[1]);
int three=Integer.parseInt(values[2]);
int four=Integer.parseInt(values[3]);
return (one<<24)+(two<<16)+(three<<8)+four;
}
public static String intToIp(int value){
StringBuilder builder=new StringBuilder();
int one=(value&0xff000000)>>24;
int two=(value&0x00ff0000)>>16;
int three=(value&0x0000ff00)>>8;
int four=(value&0x000000ff);
builder.append(one).append('.').append(two).append('.')
.append(three).append('.').append(four);
return builder.toString();
}
public static void main(String[] args){
Scanner in = new Scanner(System.in);
String ip=in.next();
int value=in.nextInt();
System.out.println(ipToInt(ip));
System.out.println(intToIp(value));
}
}統計每個月兔子的總數
import java.util.Scanner;
public class Main {
public static void main(String[] args){
Scanner in = new Scanner(System.in);
int month=in.nextInt();
int age1=1,age2=0,age3=0;//分別代表各個年齡兔子個數
for(int m=2;m<=month;m++){
age3+=age2;//先計算age3
int newCount=age3;//再計算新的age1
age2=age1;
age1=newCount;
}
System.out.print(age1+age2+age3);
}
}但是，你不一定能一眼看出問題的本質，還是得掌握基本求解思路。
求小球落地5次後所經歷的路程和第5次反彈的高度
import java.util.Scanner;
public class Main {
public static void main(String[] args){//畫圖輔助思路
Scanner in = new Scanner(System.in);
double height=in.nextDouble(); //高度
double res=height;//路徑長度
height/=2;
for(int i=1;i<=4;i++){
res+=height*2;
height/=2;
}
System.out.println(res);
System.out.println(height);
}
}迷宮問題
<pre name="code" class="java">import java.util.HashSet;
import java.util.Scanner;
import java.util.Stack;
public class Main {
private static class Point{
public int m;
public int n;
Point pre=null;//前驅座標
public Point(int m,int n){
this.m=m;
this.n=n;
}
//重寫
@Override
public boolean equals(Object obj){
Point comp=(Point)obj;
if(this.m==comp.m&&this.n==comp.n){
return true;
}else{
return false;
}
}
@Override
public int hashCode(){
return m*1000+n;
}
}
public static void main(String[] args){
Scanner in = new Scanner(System.in);
int m=in.nextInt(),n=in.nextInt();
int[][] a=new int[m][n];
for(int i=0;i<m;i++){
for(int j=0;j<n;j++){
a[i][j]=in.nextInt();
}
}
HashSet<Point> finds=new HashSet<Point>();//已經可達的點
finds.add(new Point(0,0));//初始化
Point end=new Point(m-1,n-1);
while(!finds.contains(end)){//寬度優先遍歷
HashSet<Point> newPoints=new HashSet<Point>(); //下一步可達的點
for(Point p:finds){
if(p.m>0){//上
Point t=new Point(p.m-1,p.n);
if(!finds.contains(t)&&!newPoints.contains(t)&&a[t.m][t.n]==0){
t.pre=p;
newPoints.add(t);
}
}
if(p.m<m-1){//下
Point t=new Point(p.m+1,p.n);
if(!finds.contains(t)&&!newPoints.contains(t)&&a[t.m][t.n]==0){
t.pre=p;
newPoints.add(t);
}
if(t.equals(end)){
end=t;
break;
}
}
if(p.n>0){//左
Point t=new Point(p.m,p.n-1);
if(!finds.contains(t)&&!newPoints.contains(t)&&a[t.m][t.n]==0){
t.pre=p;
newPoints.add(t);
}
}
if(p.n<n-1){//右
Point t=new Point(p.m,p.n+1);
if(!finds.contains(t)&&!newPoints.contains(t)&&a[t.m][t.n]==0){
t.pre=p;
newPoints.add(t);
}
if(t.equals(end)){
end=t;
break;
}
}
}
for(Point np:newPoints){//加入新找到的點
finds.add(np);
}
}
Stack<Point> stack=new Stack<Point>();//倒敘輸出
Point p=end;
while(p!=null){
stack.push(p);
p=p.pre;
}
while(!stack.isEmpty()){
Point loc=stack.pop();
System.out.println("("+loc.m+","+loc.n+")");
}
}
}Sudoku-java
import java.util.ArrayList;
import java.util.Scanner;
public class Main{
private static boolean solve(char[][] board,int index,ArrayList<ArrayList<Integer>> emptyLocations){
if(index==emptyLocations.size()){
return true;
}
ArrayList<Integer> location=emptyLocations.get(index);
int row=location.get(0),col=location.get(1);
for(char c='1';c<='9';c++){
if(isValid(board,row,col,c)){
board[row][col]=c;
if(solve(board,index+1,emptyLocations)){
return true;
}else{
board[row][col]='.';
}
}
}
return false;
}
public static boolean isValid(char[][] board,int row,int col,char c){
//驗證行
for(int i=0;i<9;i++){
if(board[row][i]==c)
return false;
}
//驗證列
for(int i=0;i<9;i++){
if(board[i][col]==c)
return false;
}
//驗證3*3格子
for(int i=(row/3)*3;i<(row/3)*3+3;i++){
for(int j=(col/3)*3;j<(col/3)*3+3;j++){
if(board[i][j]==c)
return false;
}
}
return true;
}
public static void solveSudoku(char[][] board) {
ArrayList<ArrayList<Integer>> emptyLocations=
new ArrayList<ArrayList<Integer>>();
for(int row=0;row<9;row++){
for(int col=0;col<9;col++){
if(board[row][col]=='.'){
ArrayList<Integer> location=new ArrayList<Integer>();
location.add(row);location.add(col);
emptyLocations.add(location);
}
}
}
solve(board,0,emptyLocations);
}
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
char[][] board=new char[9][9];
for(int i=0;i<9;i++){
for(int j=0;j<9;j++){
char c=(char) (in.nextInt()+'0');
if(c=='0'){
board[i][j]='.';
}else{
board[i][j]=c;
}
}
}
solveSudoku(board);
for(int i=0;i<9;i++){
for(int j=0;j<8;j++){
System.out.print(board[i][j]+" ");
}
System.out.print(board[i][8]);
System.out.println();
}
}
}計算字串的距離（編輯距離）
分析 動態規劃演算法。 遞迴版本：import java.util.Scanner;
public class Main {
private static int distanceOf(String a,int endA,String b,int endB){
if(endA<endB){//保證a比b長
int t=endA;endA=endB;endB=t;
String ts=a;a=b;b=ts;
}
if(endB==-1)return endA+1;//如果較短的為空，返回較長的長度
if(a.charAt(endA)==b.charAt(endB)){//末尾相等
return distanceOf(a,endA-1,b,endB-1);
}else{
return 1+Math.min(distanceOf(a,endA-1,b,endB-1),distanceOf(a,endA-1,b,endB));
}
}
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
String a=in.next();
String b=in.next();
System.out.println(distanceOf(a,a.length()-1,b,b.length()-1));
}
} import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
String a=in.next();
String b=in.next();
int m=a.length(),n=b.length();
int[][] d=new int[m+1][n+1];
for(int i=0;i<=m;i++)d[i][0]=i; //空串與其他字串編輯距離的含義
for(int j=0;j<=n;j++) d[0][j]=j;
for(int i=1;i<=m;i++){
for(int j=1;j<=n;j++){
if(a.charAt(i-1)==b.charAt(j-1)){
d[i][j]=d[i-1][j-1];
}else{
d[i][j]=1+Math.min(d[i-1][j-1], Math.min(d[i-1][j], d[i][j-1]));
}
}
}
System.out.println(d[m][n]);
}
} 四則運算
注意 1、考慮負整數的處理。 2、將各種形式的括號都看成“(”和“)”，簡化處理。import java.util.ArrayList;
import java.util.Scanner;
import java.util.Stack;
public class Main {
/** 將字串轉化成List */
public static ArrayList<String> getStringList(String str){
ArrayList<String> result = new ArrayList<String>();
StringBuilder num =new StringBuilder();
char pre='(';
for (int i = 0; i < str.length(); i++) {
char c=str.charAt(i);
if(Character.isDigit(c)||c=='-'){
if(c=='-'&&Character.isDigit(pre)){
//當前為“-”且前面為數字，為運算子
result.add(num.toString());
num.setLength(0);
result.add(str.charAt(i) + "");
}else{//普通數字或者數字的符號
num.append(c);
}
}else{
if(num.length()!=0){
result.add(num.toString());
num.setLength(0);
}
result.add(str.charAt(i) + "");
}
pre=c;
}
if(num.length() != 0){//對最後一個數做處理
result.add(num.toString());
num.setLength(0);
}
return result;
}
/**比較運算子等級 */
public static boolean compare(String peek, String cur){
if("*".equals(peek) && ("/".equals(cur) || "*".equals(cur) ||"+".equals(cur) ||"-".equals(cur))){
return true;
}else if("/".equals(peek) && ("/".equals(cur) || "*".equals(cur) ||"+".equals(cur) ||"-".equals(cur))){
return true;
}else if("+".equals(peek) && ("+".equals(cur) || "-".equals(cur))){
return true;
}else if("-".equals(peek) && ("+".equals(cur) || "-".equals(cur))){
return true;
}
return false;
}
/** 將中綴表示式轉化為字尾表示式 */
public static ArrayList<String> getPostOrder(ArrayList<String> inOrderList){
ArrayList<String> result = new ArrayList<String>();
Stack<String> stack = new Stack<String>();
for (int i = 0; i < inOrderList.size(); i++) {
String s=inOrderList.get(i);
if(Character.isDigit(s.charAt(0))||(s.length()>1&&s.charAt(0)=='-')){
//此處包括正數和負數
result.add(s);
}else{
switch (s.charAt(0)) {
case '(':
stack.push(s);
break;
case ')':
while (!stack.peek().equals("(")) {
result.add(stack.pop());
}
stack.pop();
break;
default:
while (!stack.isEmpty() && compare(stack.peek(),s)){
result.add(stack.pop());
}
stack.push(s);
break;
}
}
}
while(!stack.isEmpty()){
result.add(stack.pop());
}
return result;
}
/** 計算字尾表示式 */
public static Integer calculate(ArrayList<String> postOrder){
Stack<Integer> stack = new Stack<Integer>();
for (int i = 0; i < postOrder.size(); i++) {
String s=postOrder.get(i);
if(Character.isDigit(s.charAt(0))||(s.length()>1&&s.charAt(0)=='-')){
//此處包括正數和負數
stack.push(Integer.parseInt(postOrder.get(i)));
}else{
Integer back = (Integer)stack.pop();
Integer front = (Integer)stack.pop();
Integer res = 0;
switch (postOrder.get(i).charAt(0)) {
case '+':
res = front + back;
break;
case '-':
res = front - back;
break;
case '*':
res = front * back;
break;
case '/':
res = front / back;
break;
}
stack.push(res);
}
}
return (Integer)stack.pop();
}
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
String s=in.nextLine();//String s = "12+(23*3-56+7)*(2+90)/2";
s=s.replace('[', '(');
s=s.replace(']', ')');
s=s.replace('{', '(');
s=s.replace('}', ')');
ArrayList<String> result = getStringList(s); //String轉換為List
result = getPostOrder(result); //中綴變字尾
int i = calculate(result); //計算
System.out.println(i);
}
} 表示式求值
import java.util.ArrayList;
import java.util.Scanner;
import java.util.Stack;
public class Main {
/** 將字串轉化成List */
public static ArrayList<String> getStringList(String str){
ArrayList<String> result = new ArrayList<String>();
StringBuilder num =new StringBuilder();
for (int i = 0; i < str.length(); i++) {
char c=str.charAt(i);
if(Character.isDigit(c)){
num.append(c);
}else{
if(num.length()!=0){
result.add(num.toString());
num.setLength(0);
}
result.add(str.charAt(i) + "");
}
}
if(num.length() != 0){//對最後一個數做處理
result.add(num.toString());
num.setLength(0);
}
return result;
}
/**比較運算子等級 */
public static boolean compare(String peek, String cur){
if("*".equals(peek) && ("/".equals(cur) || "*".equals(cur) ||"+".equals(cur) ||"-".equals(cur))){
return true;
}else if("/".equals(peek) && ("/".equals(cur) || "*".equals(cur) ||"+".equals(cur) ||"-".equals(cur))){
return true;
}else if("+".equals(peek) && ("+".equals(cur) || "-".equals(cur))){
return true;
}else if("-".equals(peek) && ("+".equals(cur) || "-".equals(cur))){
return true;
}
return false;
}
/** 將中綴表示式轉化為字尾表示式 */
public static ArrayList<String> getPostOrder(ArrayList<String> inOrderList){
ArrayList<String> result = new ArrayList<String>();
Stack<String> stack = new Stack<String>();
for (int i = 0; i < inOrderList.size(); i++) {
if(Character.isDigit(inOrderList.get(i).charAt(0))){
result.add(inOrderList.get(i));
}else{
switch (inOrderList.get(i).charAt(0)) {
case '(':
stack.push(inOrderList.get(i));
break;
case ')':
while (!stack.peek().equals("(")) {
result.add(stack.pop());
}
stack.pop();
break;
default:
while (!stack.isEmpty() && compare(stack.peek(), inOrderList.get(i))){
result.add(stack.pop());
}
stack.push(inOrderList.get(i));
break;
}
}
}
while(!stack.isEmpty()){
result.add(stack.pop());
}
return result;
}
/** 計算字尾表示式 */
public static Integer calculate(ArrayList<String> postOrder){
Stack<Integer> stack = new Stack<Integer>();
for (int i = 0; i < postOrder.size(); i++) {
if(Character.isDigit(postOrder.get(i).charAt(0))){
stack.push(Integer.parseInt(postOrder.get(i)));
}else{
Integer back = (Integer)stack.pop();
Integer front = (Integer)stack.pop();
Integer res = 0;
switch (postOrder.get(i).charAt(0)) {
case '+':
res = front + back;
break;
case '-':
res = front - back;
break;
case '*':
res = front * back;
break;
case '/':
res = front / back;
break;
}
stack.push(res);
}
}
return (Integer)stack.pop();
}
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
String s=in.nextLine();//String s = "12+(23*3-56+7)*(2+90)/2";
ArrayList<String> result = getStringList(s); //String轉換為List
result = getPostOrder(result); //中綴變字尾
int i = calculate(result); //計算
System.out.println(i);
System.out.println("true");
}
} 無線OSS－高精度整數加法
import java.util.Scanner;
public class Main {
private static void reverse(char[] a){
int begin=0,end=a.length-1;
while(begin<end){
char t=a[begin];a[begin]=a[end];a[end]=t;
begin++;end--;
}
}
private static String add(String a,String b){
char[] ac=a.toCharArray();
char[] bc=b.toCharArray();
reverse(ac);
reverse(bc);//逆序，低位在前
if(ac.length<bc.length){
char[] t=ac;ac=bc;bc=t;
}//保證ac要長
char[] res=new char[ac.length];
int add=0;
for(int i=0;i<ac.length;i++){
int first=ac[i]-'0';
int second=i>=bc.length?0:bc[i]-'0';
int sum=first+second+add;
add=sum/10;
res[i]=(char)(sum%10+'0');
}
reverse(res);
return add==0?new String(res):"1"+new String(res);
}
private static String sub(String a,String b){//a比b大
char[] ac=a.toCharArray();
char[] bc=b.toCharArray();
reverse(ac);
reverse(bc);//逆序，低位在前
char[] res=new char[ac.length];
int borrow=0;//借位
for(int i=0;i<ac.length;i++){
int first=ac[i]-'0'-borrow;
int second=i>=bc.length?0:bc[i]-'0';
if(first<second){
borrow=1;
res[i]=(char)(10+first-second+'0');
}else{
res[i]=(char)(first-second+'0');
}
}
boolean find=false;
StringBuilder builder=new StringBuilder();
for(int i=res.length-1;i>=0;i--){//過濾掉高位的零
if(find==false){
if(res[i]!='0'){
find=true;
builder.append(res[i]);
}
}else{
builder.append(res[i]);
}
}
return builder.toString();
}
private static int compare(String a,String b){
if(a.length()!=b.length()){
return a.length()<b.length()?-1:1;
}
for(int i=0;i<a.length();i++){
if(a.charAt(i)!=b.charAt(i)){
return a.charAt(i)<b.charAt(i)?-1:1;
}
}
return 0;
}
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
String numA=in.next();
String numB=in.next();
int signA=1,signB=1;
if(numA.charAt(0)=='-'){
signA=-1;
numA=numA.substring(1);
}
if(numB.charAt(0)=='-'){
signB=-1;
numB=numB.substring(1);
}
if(signA==signB){//符號相同做加法
System.out.println(signA==1?add(numA,numB):"-"+add(numA,numB));
}else{//異號做減法
if(signA==-1){//使得numA為正數，numB為負數
signA=1;signB=-1;
String t=numA;numA=numB;numB=t;
}
int resSign=compare(numA,numB);
if(resSign==0){
System.out.println("0");
}else{
if(resSign<0){//結果為負數
System.out.println("-"+sub(numB,numA));
}else{//結果為整數
System.out.println(sub(numA,numB));
}
}
}
}
} 查詢兩個字串a,b中的最長公共子串
import java.util.Scanner;
public class Main{
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
String a=in.next();
String b=in.next();
int m=a.length(),n=b.length();
int[][] d=new int[m+1][n+1]; //d[i][j]表示以a[i]結尾的子串與b[j]結尾的子串的最長公共長度
int max=0,maxEnd = 0;
for(int i=1;i<=m;i++){
for(int j=1;j<=n;j++){
if(a.charAt(i-1)==b.charAt(j-1)){
d[i][j]=d[i-1][j-1]+1;
if(d[i][j]>max){
max=d[i][j];
maxEnd=i;
}
}else{
d[i][j]=0;
}
}
}
System.out.print(a.substring(maxEnd-max,maxEnd));
}
} 成績排序
import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;
public class Main {
static int mark=0;
private static class Student implements Comparable{
String name;
int score;
Student(String name,int score){
this.name=name;
this.score=score;
}
@Override
public int compareTo(Object obj) {
Student comp=(Student)obj;
int res=-1;
if(this.score==comp.score){
if(this.name.toLowerCase().compareTo(comp.name.toLowerCase())==0){//忽略大小寫比較
return 0;
}else{
res=this.name.toLowerCase().compareTo(comp.name.toLowerCase())<0?-1:1;
}
}else{
res=this.score<comp.score?-1:1;
}
return mark==1?res:res*-1;
}
}
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
int n=in.nextInt();
mark=in.nextInt();
if(n<=0) return;
ArrayList<Student> list=new ArrayList<Student>();
for(int i=0;i<n;i++){
Student t=new Student(in.next(),in.nextInt());
list.add(t);
}
Collections.sort(list);
for(Student s:list){
System.out.println(s.name+" "+s.score);
}
}
} 引數解析
import java.util.LinkedList;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sca=new Scanner(System.in);
LinkedList<String> commands=new LinkedList<String>();
while(sca.hasNext()){
commands.add(sca.next());
}
if(commands.size()==0) {System.out.println(0);return;}
int index=0;
while(index<commands.size()){
String s=commands.get(index);
if(s.charAt(0)!='\"'){//簡單命令不做任何處理
index++;
}else{
if(s.charAt(0)=='\"'&&s.charAt(s.length()-1)=='\"'){//兩頭都是"，去掉兩頭的"
commands.set(index, s.substring(1,s.length()-1));
index++;
}else{//只有一頭是",將後續的字串拼接過來
commands.set(index, s+" "+commands.get(index+1));
commands.remove(index+1);
}
}
}
System.out.println(commands.size());
for(String command:commands){
System.out.println(command);
}
}
}字串運用-密碼擷取
分析
該問題就是最長迴文子串的問題。可以採用動態規劃演算法。
除了採用動態規劃演算法，還可以採用中心擴充套件法：即依次以每個字元為中心向兩邊擴充套件，尋找最長迴文長度。
import java.util.Scanner;
public class Main {
private static int longestPalindrome(String s){
int n=s.length(),max=1;
if(n==0)return 0;
boolean[][] d=new boolean[n][n];
for(int i=0;i<n;i++){
d[i][i]=true;
}
for(int i=n-2;i>=0;i--){
for(int j=i+1;j<n;j++){
if(s.charAt(i)==s.charAt(j)){//首尾相等
if(i+1==j||d[i+1][j-1]==true){
d[i][j]=true;
max=Math.max(max, j-i+1);
}
}
}
}
return max;
}
public static void main(String[] args) {
Scanner sca=new Scanner(System.in);
String s=sca.next();
System.out.println(longestPalindrome(s));
}
}24點
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;
import java.util.Stack;
public class Main {
//比較符號優先順序
public static boolean compare(String peek, String cur){
if("*".equals(peek) && ("/".equals(cur) || "*".equals(cur) ||"+".equals(cur) ||"-".equals(cur))){
return true;
}else if("/".equals(peek) && ("/".equals(cur) || "*".equals(cur) ||"+".equals(cur) ||"-".equals(cur))){
return true;
}else if("+".equals(peek) && ("+".equals(cur) || "-".equals(cur))){
return true;
}else if("-".equals(peek) && ("+".equals(cur) || "-".equals(cur))){
return true;
}
return false;
}
// 將中綴表示式轉化為字尾表示式
public static ArrayList<String> getPostOrder(List<String> inOrderList){
ArrayList<String> result = new ArrayList<String>();
Stack<String> stack = new Stack<String>();
for (int i = 0; i < inOrderList.size(); i++) {
if(Character.isDigit(inOrderList.get(i).charAt(0))){
result.add(inOrderList.get(i));
}else{
switch (inOrderList.get(i).charAt(0)) {
case '(':
stack.push(inOrderList.get(i));
break;
case ')':
while (!stack.peek().equals("(")) {
result.add(stack.pop());
}
stack.pop();
break;
default:
while (!stack.isEmpty() && compare(stack.peek(), inOrderList.get(i))){
result.add(stack.pop());
}
stack.push(inOrderList.get(i));
break;
}
}
}
while(!stack.isEmpty()){
result.add(stack.pop());
}
return result;
}
// 計算字尾表示式
public static Integer calculate(ArrayList<String> postOrder){
Stack<Integer> stack = new Stack<Integer>();
for (int i = 0; i < postOrder.size(); i++) {
if(Character.isDigit(postOrder.get(i).charAt(0))){
stack.push(Integer.parseInt(postOrder.get(i)));
}else{
Integer back = (Integer)stack.pop();
Integer front = (Integer)stack.pop();
Integer res = 0;
switch (postOrder.get(i).charAt(0)) {
case '+':
res = front + back;
break;
case '-':
res = front - back;
break;
case '*':
res = front * back;
break;
case '/':
//如果除數為0、除數小於被除數、被除數不能被整除不是合法的計算方式
if(back==0||front<back||front%back!=0)return 0;
res = front / back;
break;
}
stack.push(res);
}
}
return (Integer)stack.pop();
}
//獲取全排列
private static List<List<String>> getAllPermutation(ArrayList<String> values){
List<List<String>> res=new ArrayList<List<String>>();
doPermutation(res,values,0);
return res;
}
private static void doPermutation(List<List<String>> res,ArrayList<String> values,int index ){
if(index==values.size()-1){
@SuppressWarnings("unchecked")
ArrayList<String> r=(ArrayList<String>) values.clone();
res.add(r);
return;
}
for(int i=index;i<values.size();i++){
Collections.swap(values, index, i);
doPermutation(res,values,index+1);
Collections.swap(values, index, i);
}
}
@SuppressWarnings("resource")
public static void main(String[] args) {
Scanner sca=new Scanner(System.in);
ArrayList<String> values=new ArrayList<String>();//數值集合
for(int i=0;i<4;i++){
String s=sca.next();
if(s.equals("joker")||s.equals("JOKER")){//非法輸入檢查
System.out.println("ERROR");
return;
}else{
char c=s.charAt(0);
if('2'<=c&&c<='9'){
values.add(s);
}else{
if(s.equals("10"))values.add(s);
if(c=='A')values.add("1");
if(c=='J')values.add("11");
if(c=='Q')values.add("12");
if(c=='K')values.add("13");
}
}
}
List<List<String>> allValues=getAllPermutation(values);//獲取數字的全排列
String[] operators={"+","-","*","/"};
for(List<String> list:allValues){//測試數字組合
for(int i=0;i<4;i++){//測試各種符號組合
for(int j=0;j<4;j++){
for(int k=0;k<4;k++){
List<String> expression=new ArrayList<String>();
expression.add(list.get(0));
expression.add(operators[i]);
expression.add(list.get(1));
expression.add(operators[j]);
expression.add(list.get(2));
expression.add(operators[k]);
expression.add(list.get(3));
//計算表示式
Integer res =calculate(getPostOrder(expression));
if(res.equals(24)){
for(String s:expression){
System.out.print(s);
}
return;
}
}
}
}
}
System.out.println("NONE");
}
}201301 JAVA 題目2-3級
分析
動態規劃。
定義：d[i][j]表示從點a[0][0]到點a[i][j]的所有路徑數。
遞推表示式：d[i][j]=d[i-1][j]+d[i][j-1]
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sca=new Scanner(System.in);
int m=sca.nextInt()+1,n=sca.nextInt()+1;//邊緣線轉換成點
int[][] d=new int[m+1][n+1];
d[1][1]=1;
for(int i=1;i<=m;i++){
for(int j=1;j<=n;j++){
if(i==1&&j==1){continue;}
d[i][j]=d[i-1][j]+d[i][j-1];
}
}
System.out.println(d[m][n]);
}
}輸入整型陣列和排序標識，對其元素按照升序或降序進行排序
public class Main {
private static int mark=0;
public static class MyComparator implements Comparator{
@Override
public int compare(Object arg0, Object arg1) {
int a=(int)arg0,b=(int)arg1;
if(a==b) return 0;
if(a<b){
return mark==0?-1:1;
}else{
return mark==0?1:-1;
}
}
}
public static void main(String[] args) {
Scanner sca=new Scanner(System.in);
int n=sca.nextInt();
ArrayList<Integer> nums=new ArrayList<Integer>();
for(int i=0;i<n;i++){
nums.add(sca.nextInt());
}
mark=sca.nextInt();
Collections.sort(nums, new MyComparator());
for(int i=0;i<n-1;i++){
System.out.print(nums.get(i)+" ");
}
System.out.print(nums.get(n-1));
}
} Redraiment的走法
分析
該問題實質上就是求最長上升子序列的問題。採用動態規劃演算法。
定義：d[i]表示以a[i]結尾的最長上升子序列長度。
遞推表示式：d[i]=max{d[j]+1}，d[j]<d[i]且j<i
import java.text.DecimalFormat;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sca=new Scanner(System.in);
int n=sca.nextInt(),res=1;
int[] heights=new int[n];
int[] counts=new int[n];//表示以heights[i]結尾的最長上升序列長度
for(int i=0;i<n;i++){
heights[i]=sca.nextInt();
counts[i]=1;
}
for(int i=1;i<n;i++){
int max=0;
for(int j=0;j<i;j++){
if(heights[j]<heights[i]){//前面的小於當前元素
max=Math.max(max, counts[j]);
}
}
counts[i]=max+1;
res=Math.max(res, counts[i]);
}
System.out.print(res);
}
}字串分割
import java.util.Scanner;
public class Main {
private static String zeroStr(int n){
StringBuilder builder=new StringBuilder();
for(int i=0;i<n;i++){
builder.append('0');
}
return builder.toString();
}
private static void printStr(String s){
int begin=0;
while(begin<s.length()){
System.out.println(s.substring(begin,begin+8));
begin+=8;
}
}
public static void main(String[] args) {
Scanner sca=new Scanner(System.in);
int n=sca.nextInt();
if(n<=0) return;
for(int i=0;i<n;i++){
String s=sca.next();
if(s.length()%8!=0){
s+=zeroStr(8-s.length()%8);
}
printStr(s);
}
}
} 記負均正
import java.text.DecimalFormat;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sca=new Scanner(System.in);
int navigateCount=0,positiveCount=0;
double sum=0.0;
while(sca.hasNext()){
int i=sca.nextInt();
if(i<0){
navigateCount++;
}else{
positiveCount++;
sum+=i;
}
}
double average=positiveCount==0?0.0:sum/positiveCount;//防止除數為零
DecimalFormat df=new DecimalFormat("#.0"); //保留一位小數
System.out.println(navigateCount);
System.out.println(df.format(average));
}
}字串分割
分析
先對每個輸入字串進行補齊，然後統一分割。
import java.util.Scanner;
public class Main {
private static String zeroStr(int n){
StringBuilder builder=new StringBuilder();
for(int i=0;i<n;i++){
builder.append('0');
}
return builder.toString();
}
private static void printStr(String s){
int begin=0;
while(begin<s.length()){
System.out.println(s.substring(begin,begin+8));
begin+=8;
}
}
public static void main(String[] args) {
Scanner sca=new Scanner(System.in);
while(sca.hasNext()){
String s=sca.next();
if(s.length()%8!=0){
s+=zeroStr(8-s.length()%8);
}
printStr(s);
}
}
}