C++ primer 第五版第六章练习答案

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Shengjianjun 2023-01-12 05:48:53 ©著作权

文章标签 C++ #include ios ci 文章分类 运维

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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 once
int 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 once
bool 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;
}