java三種排序及二維陣列
阿新 • • 發佈：2018-11-02
排序
氣泡排序
public class TestDemo {
//氣泡排序
public static void bubbleSort(int[] array) {
boolean val = false;
for (int i = 0; i < array.length - 1; i++) {
for (int j = 0; j < array.length - 1 - i; j++) {
if (array[j] > array[j + 1]) {
int 時間複雜度：
最好情況 O(n) 當輸入的陣列有序就是最好情況
最壞情況 O(n^2)
穩定性：在輸入陣列中有兩個及以上相同的數，排序結束後數字前後位置不變
穩定
直接插入排序
public class TestDemo {
//直接插入排序
public static void insertSort(int[] 時間複雜度：
最好情況 O(n)
最壞情況 O(n^2)
穩定性：穩定
選擇排序
public class TestDemo {
//選擇排序
public static void selectSort(int[] array) {
for (int i = 0; i < array.length; i++) {
for (int j = i + 1; j < array.length; j++) {
if (array[i] > array[j]) {
int tmp = array[j];
array[j] = array[i];
array[i] = tmp;
}
}
}
}
public static void main(String[] args) {
int[] array = {1, 5, 15, 2, 9, 6, 35, 22};
selectSort(array);
System.out.println(Arrays.toString(array));
}
}
時間複雜度：： O(n^2)
穩定性：穩定
二維陣列
定義
int[][] array = new int[2][3];
//第一種
int[][] array2 = {{1,2,3},{4,5,6},{7,8,9}};
//第二種
int[][] array3 = new int[2][];
array3[0] = new int[4];
array3[1] = new int[5];
//定義一個不規則陣列
二維陣列的拷貝
與一維陣列相同，四種拷貝方式皆為淺拷貝
以下四種方法二維陣列array1的初始值為10
for迴圈拷貝
class Arr {
private int val = 10;
public void setVal(int val) {
this.val = val;
}
public int getVal() {
return this.val;
}
}
public class TestDemo1 {
public static void main(String[] args) {
Arr[][] array1 = new Arr[2][2];
array1[0][0] = new Arr();
array1[0][1] = new Arr();
array1[1][0] = new Arr();
array1[1][1] = new Arr();
Arr[][] array2 = new Arr[2][2];
for (int i = 0; i < array1.length; i++) {
for (int j = 0; j < array1[i].length; j++) {
array2[i][j] = array1[i][j];
}
}
for (int i = 0; i < array2.length; i++) {
for (int j = 0; j < array2[i].length; j++) {
System.out.print(array2[i][j].getVal() + " ");
}
System.out.println();
}
array2[0][0].setVal(100);
System.out.println("================修改後===============");
for (int i = 0; i < array2.length; i++) {
for (int j = 0; j < array2[i].length; j++) {
System.out.print(array2[i][j].getVal() + " ");
}
System.out.println();
}
System.out.println();
}
}
輸出結果：
.clone()
class Arr {
private int val = 10;
public void setVal(int val) {
this.val = val;
}
public int getVal() {
return this.val;
}
}
public class TestDemo1 {
public static void main(String[] args) {
Arr[][] array1 = new Arr[2][2];
array1[0][0] = new Arr();
array1[0][1] = new Arr();
array1[1][0] = new Arr();
array1[1][1] = new Arr();
Arr[][] array2 = new Arr[2][2];
for (int i = 0; i < array1.length; i++) {
array2[i] = array1[i].clone();
for (int j = 0; j < array1[i].length; j++) {
System.out.print(array2[i][j].getVal() + " ");
}
System.out.println();
}
array2[0][0].setVal(100);
System.out.println("================修改後===============");
for (int i = 0; i < array2.length; i++) {
for (int j = 0; j < array2[i].length; j++) {
System.out.print(array2[i][j].getVal() + " ");
}
System.out.println();
}
}
}
輸出結果:
Arrays.cpoyOf()
class Arr {
private int val = 10;
public void setVal(int val) {
this.val = val;
}
public int getVal() {
return this.val;
}
}
public class TestDemo1 {
public static void main(String[] args) {
Arr[][] array1 = new Arr[2][2];
array1[0][0] = new Arr();
array1[0][1] = new Arr();
array1[1][0] = new Arr();
array1[1][1] = new Arr();
Arr[][] array2 = new Arr[2][2];
//array2 = Arrays.copyOf(array1, array1.length);
//或者將迴圈中的Arrays.copyOf方法刪掉，用上一行的方法拷貝
for (int i = 0; i < array1.length; i++) {
array2[i] = Arrays.copyOf(array1[i], array1[i].length);
for (int j = 0; j < array1[i].length; j++) {
// array2[j]=array1[j].clone();
System.out.print(array2[i][j].getVal() + " ");
}
System.out.println();
}
array2[0][0].setVal(100);
System.out.println("================修改後===============");
for (int i = 0; i < array2.length; i++) {
for (int j = 0; j < array2[i].length; j++) {
System.out.print(array2[i][j].getVal() + " ");
}
System.out.println();
}
}
}
輸出結果：
System.arraycopy()
class Arr {
private int val = 10;
public void setVal(int val) {
this.val = val;
}
public int getVal() {
return this.val;
}
}
public class TestDemo1 {
public static void main(String[] args) {
Arr[][] array1 = new Arr[2][2];
array1[0][0] = new Arr();
array1[0][1] = new Arr();
array1[1][0] = new Arr();
array1[1][1] = new Arr();
Arr[][] array2 = new Arr[2][2];
for (int i = 0; i < array1.length; i++) {
System.arraycopy(array1[i], 0, array2[i], 0, array1[i].length);
for (int j = 0; j < array1[i].length; j++) {
System.out.print(array2[i][j].getVal() + " ");
}
System.out.println();
}
array2[0][0].setVal(100);
System.out.println("================修改後===============");
for (int i = 0; i < array2.length; i++) {
for (int j = 0; j < array2[i].length; j++) {
System.out.print