C++ Primer 第五版第三章習題答案
阿新 • • 發佈：2018-12-25
書籍版本：2019年9月第一版；王剛 楊巨峰譯；電子工業出版社
編譯器 ： win10 && VS2015
3.1
對之前的練習用using來宣告，其餘與之前一致。
3.2
#include "stdafx.h" #include <iostream> #include <string> using namespace std; int main() { //string line; // 按行讀入 //while(getline(cin,line)) //{ // cout << line << endl; //} // 按詞讀入 string word; while(cin>>word) { cout << word << endl; } system("pause"); return 0; }
3.3
string類忽略遇到第一個有效字元前的所有空格，遇到第一個有效字元之後所有空格都開始有效
getline跳過空格繼續向下讀取
3.4
#include "stdafx.h" #include <iostream> #include <string> using namespace std; int main() { string line1,line2; cout << "請輸入字串1："; cin >> line1; cout << "請輸入字串2："; cin >> line2; if (line1 == line2) { cout << "兩個字串相等" << endl; } else { cout << "兩個字串不相等" << endl; } if (line1.size() == line2.size()) { cout << "兩個字串長度相等" << endl; } else { cout << "兩個字串長度不相等" << endl; } system("pause"); return 0; }
3.5
#include "stdafx.h" #include <iostream> #include <string> using namespace std; int main() { string line,strNoSpace,strSpace; while (cin>>line) { if (line == "break;") { break; } strNoSpace = strNoSpace + line; strSpace = strSpace + " "; strSpace = strSpace + line; } cout << "不帶空格：" << strNoSpace << endl; cout << "帶空格：" << strSpace << endl; system("pause"); return 0; }
3.6
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
int main()
{
string str("test");
for (auto &s : str)
{
s = 'x';
}
cout << str;
system("pause");
return 0;
}
3.7
可以將型別換位char，具體操作就是將上面的auto換成char；結果無變化；
3.8
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
int main()
{
string str("test");
int i = 0;
for (i = 0;i<str.size();i++)
{
str[i] = 'x';
}
cout << "for：" << str << endl;
while (i<str.size())
{
str[i] = 'x';
}
cout << "while：" << str << endl;
system("pause");
return 0;
}
3.9
不合法，s未賦初始值為空，沒有s[0];
3.10
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
int main()
{
string str("test,test,test");
int i = 0;
for (i = 0;i<str.size();i++)
{
if ( ispunct(str[i]) )
{
str[i] = ' ';
for (int j = i; j < str.size(); j++)
{
str[j] = str[j + 1];
}
}
}
cout << str << endl;
system("pause");
return 0;
}
3.11
合法，型別為char
3.12
a 正確，建立了一個裡面是整形向量的向量；
b 錯誤，型別不同無法拷貝
c 正確，建立了一個string向量，裡面有10個值為null的string；
3.13
a 0個元素，空的
b 10個元素，都沒有值
c 10個值為42的int元素
d 1個值為10的元素
e 兩個元素，一個值為10，另一個為42
f 10個值為空的string元素，因為10不是string
g 10個值為hi的string元素；
3.14
#include "stdafx.h"
#include <iostream>
#include <vector>
using namespace std;
int main()
{
int num;
vector<int> vec;
while (cin>>num)
{
vec.push_back(num);
}
system("pause");
return 0;
}
3.15
#include "stdafx.h"
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
string str;
vector<string> strVec;
while (cin>>str)
{
strVec.push_back(str);
}
system("pause");
return 0;
}
3.16
我之前的結果是對的，檢驗過了
3.17
#include "stdafx.h"
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
string str;
vector<string> strVec;
while (cin>>str)
{
if (str == "break;")
{
break;
}
strVec.push_back(str);
}
for (int i = 0; i < strVec.size(); i++)
{
string strC = strVec.at(i);
for (int j = 0; j < strC.size(); j++)
{
toupper(strC[j]);
}
cout << strC << endl;
}
system("pause");
return 0;
}
3.18
不合法，改成
vector<int> ivec;
int num = 42;
ivec.push_back(num);
3.19
vector<int> numVec(10, 42);
vector<int> numVec{42,42,42,42,42,42,42,42,42,42};
vector<int> numVec;
int num = 42;
for(int i = 0;i<10;i++)
{
ivec.push_back(num);
}
3.20
#include "stdafx.h"
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
string str;
vector<int> strVec;
int num[10] = { 1,2,3,4,5,6,7,8,9 };
int m = 0;
while (m<10)
{
strVec.push_back(num[m]);
m++;
}
cout << "相連兩個：";
for (int i = 0; i < strVec.size()-1; i++)
{
cout << strVec[i] + strVec[i + 1] << " ";
}
cout << endl;
cout << "頭尾兩個：";
for (int i = 0; i < strVec.size(); i++)
{
cout << strVec[i] + strVec[strVec.size()-1-i-1] << " ";
}
cout << endl;
system("pause");
return 0;
}
3.21
#include "stdafx.h"
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
string str;
vector<int> strVec;
int num[10] = { 1,2,3,4,5,6,7,8,9,11 };
int m = 0;
while (m<10)
{
strVec.push_back(num[m]);
m++;
}
vector<int>::iterator it;
for (it = strVec.begin(); it != strVec.end(); it++)
{
cout << *it << endl;
}
system("pause");
return 0;
}
3.22
#include "stdafx.h"
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
string str("test,test");
for (auto it = str.begin(); it != str.end(); it++)
{
*it = toupper(*it);
cout << *it ;
}
system("pause");
return 0;
}
3.23
=
#include "stdafx.h"
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
string str;
vector<int> strVec = {1,2,3,4,5,6,7,8,9,10};
vector<int>::iterator it;
for (it = strVec.begin(); it != strVec.end(); it++)
{
*it = *it * 2;
cout << *it << endl;
}
system("pause");
return 0;
}
3.24
#include "stdafx.h"
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
string str;
vector<int> strVec = {1,2,3,4,5,6,7,8,9,10};
vector<int>::iterator it;
int n = 1;
int sum;
// 連續兩個相加
for (it = strVec.begin(); it != strVec.end()-1; it++)
{
sum = *it + *(it + 1);
cout << sum << endl;
}
system("pause");
return 0;
}
3.25
#include "stdafx.h"
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
string str;
vector<int> strVec;
for (int i = 0; i < 10; i++)
{
int num;
cin >> num;
strVec.push_back(num);
}
vector<int> core(11, 0);
vector<int>::iterator it;
for (it = strVec.begin();it != strVec.end();it++)
{
int index = (*it) / 10;
core[index]++;
}
for (it = core.begin(); it != core.end(); it++)
{
cout << *it << " ";
}
system("pause");
return 0;
}
3.26
因為要求的mid是相對於從beg開始到end結束的中間值
3.27
a unsigned是非定長；
b 合法的
c 函式返回值是int型但是不是定值，所以是非定長的；
d fundamental有11個字元，字串陣列長度也設定為11缺少“\0”的位置
3.28
string sa[10] 與string sa2[10] 都為空，裡面無值
int ia[10];裡面值都為0；
int ia2[10];裡面值都為隨機值
#include "stdafx.h"
#include <iostream>
#include <string>
#include <vector>
using namespace std;
string sa[10];
int ia[10];
int main()
{
string sa2[10];
int ia2[10];
for (int i = 0; i < 10; i++)
{
cout << sa[i] << endl;
cout << ia[i] << endl;
cout << sa2[i] << endl;
cout << ia2[i] << endl;
cout << "分割線" << endl;
}
system("pause");
return 0;
}
3.29
陣列只能定長，無法自動增長，缺少靈活性，在用之前不能確定需要的空間大小時很不方便；
3.30
ix 只能小與array_size，等於時越界，因為長度為array_size的陣列下標範圍為0到array_size-1；
3.31
#include "stdafx.h"
#include <iostream>
using namespace std;
int main()
{
int a[10];
for (int i = 0; i < 10; i++)
{
a[i] = i;
}
for (int i = 0; i < 10; i++)
{
cout << a[i] << endl;
}
system("pause");
return 0;
}
3.32
#include "stdafx.h"
#include <iostream>
using namespace std;
int main()
{
int a[10];
for (int i = 0; i < 10; i++)
{
a[i] = i;
}
for (int i = 0; i < 10; i++)
{
cout << a[i] << endl;
}
int a2[10];
for (int i = 0; i < 10; i++)
{
a2[i] = a[i];
}
vector<int> vec;
for (int i = 0; i < 10; i++)
{
vec.push_back(i);
}
system("pause");
return 0;
}
3.33
不初始化裡面的值都是隨機值；
3.34
p1 += p2 - p1; 等價於 p1 = p2 - p1 + p1 = p2;
在p1p2不指向同一陣列時非法；
3.35
#include "stdafx.h"
#include <iostream>
using namespace std;
int main()
{
int a[10];
int* num = a;
for (int i = 0; i < 10; i++)
{
a[i] = 0;
cout << a[i] << endl;
}
system("pause");
return 0;
}
3.36
#include "stdafx.h"
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
int a[10],b[10];
int* numa = a;
int* numb = b;
for (int i = 0; i < 10; i++)
{
a[i] = i;
b[i] = 10 - i;
}
for (int i = 0; i < 10; i++)
{
if( *(numa+i) == *(numb+i) )
{
}
else
{
cout << "不相等" << endl;
break;
}
}
vector<int> veca(10, 1);
vector<int> vecb;
for (int i = 0; i < 10; i++)
{
vecb.push_back(i);
}
for (int i = 0; i < 10; i++)
{
if(!veca[i] == vecb[i])
{
cout << "不相等" << endl;
break;
}
}
system("pause");
return 0;
}
3.37
#include "stdafx.h"
#include <iostream>
using namespace std;
int main()
{
const char ca[] = { 'h', 'e', 'l', 'l', 'o' };
const char* cp = ca;
while (*cp)
{
cout << *cp << endl;
++cp;
}
system("pause");
return 0;
}
結果如下：
3.38
指標就是地址，兩個地址相加之後是未知的存在。
3.39
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
bool stringcomp(string str1, string str2)
{
if (str1 == str2)
{
return true;
}
else
{
return false;
}
}
bool cstringcomp(char s1[], char s2[])
{
if (strcmp(s1, s2) == 0)
{
return true;
}
else
{
return false;
}
}
int main()
{
string str1 = "hello";
string str2 = "hello!";
char ca1[] = { 'h', 'e', 'l', 'l', 'o' , '\0'};
char ca2[] = { 'h', 'e', 'l', 'l', 'o' , '!', '\0' };
cout << stringcomp(str1, str2) << endl;
cout << cstringcomp(ca1, ca2) << endl;
system("pause");
return 0;
}
3.40
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
int main()
{
char ca1[] = "hello";
char ca2[] = "world";
char str[11];
strcpy_s(str, ca1);
strcat_s(str, ca2);
cout <<str << endl;
system("pause");
return 0;
}
因為我用的是VS2015，所以會自動提示strcmp與strcat是不安全的，原因是這些函式內部是不進行引數檢測的（包括越界類的），微軟擔心使用這些會造成記憶體異常，所以就改寫了同樣功能的函式，改寫了的函式進行了引數的檢測，使用這些新的函式會更安全和便捷，而改寫後安全的函式就是strcmp_s與strcat-s。
3.41
#include "stdafx.h"
#include <iostream>
#include <vector>
using namespace std;
int main()
{
int a[6];
for (int i = 0; i < 6; i++)
{
a[i] = i;
}
vector<int> intVec(begin(a), end(a));
for (int i = 0; i < intVec.size(); i++)
{
cout << intVec.at(i) << endl;
}
system("pause");
return 0;
}
3.42
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
int main()
{
int a[6];
for (int i = 0; i < 6; i++)
{
a[i] = i;
}
vector<int> intVec(begin(a), end(a));
int a2[6];
for (int i = 0; i < intVec.size(); i++)
{
a2[i] = intVec.at(i);
cout << a2[i] << endl;
}
system("pause");
return 0;
}
3.43
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
int main()
{
int ia[3][4] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
for (const int(&p)[4] : ia)
for (int q : p) cout << q << " ";
cout << endl;
for (size_t i = 0; i != 3; ++i)
for (size_t j = 0; j != 4; ++j) cout << ia[i][j] << " ";
cout << endl;
for (int(*p)[4] = ia; p != ia + 3; ++p)
for (int* q = *p; q != *p + 4; ++q) cout << *q << " ";
cout << endl;
system("pause");
return 0;
}
3.44
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
int main()
{
int ia[3][4] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
using int_array = int[4];
for (int_array& p : ia)
for (int q : p) cout << q << " ";
cout << endl;
for (size_t i = 0; i != 3; ++i)
for (size_t j = 0; j != 4; ++j) cout << ia[i][j] << " ";
cout << endl;
for (int_array* p = ia; p != ia + 3; ++p)
for (int* q = *p; q != *p + 4; ++q) cout << *q << " ";
cout << endl;
system("pause");
return 0;
}
3.45
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
int main()
{
int ia[3][4] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
// a range for to manage the iteration
for (auto& p : ia)
for (int q : p) cout << q << " ";
cout << endl;
// ordinary for loop using subscripts
for (size_t i = 0; i != 3; ++i)
for (size_t j = 0; j != 4; ++j) cout << ia[i][j] << " ";
cout << endl;
// using pointers.
for (auto p = ia; p != ia + 3; ++p)
for (int* q = *p; q != *p + 4; ++q) cout << *q << " ";
cout << endl;
system("pause");
return 0;
}