C++ primer 第五版 第六章练习答案

6.3

#include<iostream>using namespace std;int fact(int ret) {int val = 1;while (ret > 1) {val *= ret--;}return val;}int main() {int j = fact(5);cout << j << endl;}

6.4

#include<iostream>using namespace std;int fact(int ret) {int val = 1;while (ret > 1) {val *= ret--;}return val;}int main() {cout << "请输入一个数" << endl;int num = 0;cin >> num;int j = fact(num);cout << "该数的阶乘为" << j << endl;}

6.5

#include<iostream>using namespace std;int abbs(int num) {num = abs(num);return num;}int main() {int a = 0;cin >> a;cout << abbs(a) << endl;}

6.6

#include<iostream>using namespace std;//局部变量   形参    局部静态变量int bbb(int a) {//a为形参   也是局部变量int ccc = 0;//ccc为局部静态变量++ccc;return ccc;}int main() {int m = 5;int j = 0;while (m) {--m;j = bbb(1);}cout << j << endl;//cout << ccc << endl; //局部静态变量不是指在函数外可以调用这个值，而是在这个值存在，与局部变量对比，其值不会被销毁}

6.7

#include<iostream>using namespace std;int bbb() {static int cc = -1;++cc;return cc;}int main() {int m;cin >> m;int j = 0;while (m) {--m;j = bbb();}cout << j;}

6.8

#pragma onceint f();int fact();int change();

6.9

头文件

#pragma once

int fact(int ret);

fact函数

#include "标头.h"

int fact(int ret) {

int S = 1;

while (ret != 1) {

S *= ret;--ret;

}

return S;

}

main函数

#include "标头.h"

#include <iostream>

using namespace std;

int main() {

int n = 0;

cin >> n;

int b;

b=fact(n);

cout << b << endl;

}

6.10

#include<iostream>using namespace std;void change(int *a, int*b) {int t;t = *a;*a = *b;*b = t;}int main() {int q = 5;int r = 10;int *f = &q;int *k = &r;change(f, k);cout << "f的值为" << q;cout << "k的值为" <<r;}

6.11

#include <iostream>#include <string>using namespace std;void reset(int &s) {s = 0;}int main() {int b = 48;int &y = b;reset(y);cout << b << endl;}

6.12

#include <iostream>#include <string>using namespace std;void change(int &a, int &b) {int t = a;a = b;b = t;}int main() {int q = 30;int p = 20;int &qq = q;int &pp = p;change(qq, pp);cout << "q的值为" << q;cout << "p的值为" << p;}

------自定义函数find_char自己的理解

#include <iostream>#include <string>using namespace std;//定义函数返回字符串中某个字母第一次出现的位置以及出现的次数string::size_type find_char(const string &s, char c, string::size_type &occurs) {auto ret = s.size();occurs = 0;int Cnt = 0;for (auto q : s) {++Cnt;if (q == c) {if (ret == s.size())ret = Cnt;++occurs;}}return ret;}int main() {string text = "";cin >> text;const string &ss = text;char f = 'q';string::size_type occurs = 45;string::size_type &t = occurs;int b=find_char(ss, f, t);cout << "q的出现次数为" << occurs<<endl;cout << "q第一次出现的位置为" << b;}

6.17

#include <iostream>#include <string>using namespace std;bool if_Cap(const string &s) {for (auto q : s) {int a = q;if (a>=65&&a<=90){return false;}}return true;}void Cap(string &s) {for (auto &q : s) {int a = q;if (a >= 97 && a <= 122) {q = a - 32;}}}int main() {string text = "";cin >> text;const string &s = text;if (if_Cap(s)) {cout << "无大写字母" << endl;}else {cout << "有大写字母" << endl;}string &f = text;Cap(f);cout << text << endl;}

6.18

#pragma oncebool compare(const matrix &x, const matrix &y);int change_val(int x,vector<int>itrtator it);

6.21

#include <iostream>using namespace std;int Max(int a,int*b) {if (a>* b) {return a;}return *b;}int main() {int a = 10;int b = 20;int *c = &b;cout << Max(a, c) << endl;}

6.22

#include <iostream>using namespace std;void change(int **a, int **b) {int **c=&*a;*c = *a;*a = *b;*b = *c;}int main() {int a = 20;int b = 60;int *aa = &a;int *bb = &b;int **aaa = &aa;int **bbb = &bb;change(aaa, bbb);cout << "*aa的值为" << *aa;*aa = 98;cout << b << endl;}

6.23

#include <iostream>using namespace std;int print(int *f, int n) {for (int i = 0; i < n; ++i) {cout << f[i] << endl;}}

6.25

#include <iostream>#include <string>using namespace std;int main(int argc,char **argv) {string str1 = "";string str2 = "";str1 = argv[1];str2 = argv[2];str1 += str2;cout << str1;}

6.26

#include <iostream>#include <string>using namespace std;int main(int argc,char **argv) {for (int i = 0; i < argc; ++i) {cout << argv[i] << endl;}}

6.27

#include <iostream>#include <initializer_list>using namespace std;int Sum(initializer_list<int>lst) {int sum = 0;for (auto q : lst) {sum += q;}return sum;}

6.30

#include <iostream>#include <string>using namespace std;bool str_subrange(const string &str1, const string &str2) {if (str1.size() == str2.size()) {return str1 == str2;}auto size = (str1.size() < str2.size()) ? str1.size() : str2.size();//得到较短的string长度for (decltype(size)i = 0; i != size; ++i) {if (str1[i] != str2[i])return 0;}return 0;}int main() {string text = "i love you";string text1 = "me too";cout << str_subrange(text, text1);}

6.33

#include <iostream>#include <string>#include <vector>using namespace std;//递归输出vector对象int cc(vector<int>q) {if (q.size() != 0) {cout << q.back()<<endl;q.pop_back();cc(q);}return 0;}int main() {vector<int>ivec = { 0,1,2,3,4 };cc(ivec);}

6.36

#include <iostream>#include <string>using namespace std;/*string odd[] = { "1","2","3","4","5" };string &k(string a[]) {}*/string(*fun(string i))[10];//最内层string i表示调用函数时需要的是string类型的实参，外面的*表示对函数调用的结果执行解引用操作，后面的[10]表示调用将得到一个维度为10的数组，最前面的string则表示返回数组元素的类型为sting类型

6.37

1----使用尾置返回类型

#include <iostream>#include <string>using namespace std;auto func(string i)->string(*)[10];

2----使用decltype

#include <iostream>#include <string>using namespace std;string arr[10] = {};decltype(arr)*arrptr(string i);

3----使用类型别名

#include <iostream>#include <string>using namespace std;typedef string arr[10];//arr m = { "12","re" };arr(*fun(string i));

6.38

#include <iostream>#include <string>using namespace std;int odd[] = { 1,3,5,7,9 };int even[] = { 0,2,4,6,8 };decltype(odd)&arrPtr(int i) {return(i % 2) ? odd : even;}//我他妈就是个天才

函数重载

#include <iostream>#include <string>using namespace std;void print(string i) {cout << "!";}void print(int i) {cout << "?";}void print(double q) {cout << "#";}int main() {//string i = "";int i = 30;print(i);}

6.42

#include <iostream>#include <string>using namespace std;string make_plural(size_t ctr, const string &word, const string &ending = "s") {return (ctr > 1) ? word + ending : word;}