函数巩固

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 int add(int num)//按值传递
 4 {
 5     num++;
 6 }
 7 int add1(int& num)//参数传递（引用传递）
 8 {
 9     num++;
10 }
11 
12 int main()
13 {
14     int num = 10;
15     add(num);//按值传递，传递的num是一个副本，地址空间相与之前发生了变化
16     cout << num << endl;//10
17     add1(num);//引用传递，num是原数据的别名，地址相同
18     cout << num << endl;//11
19     return 0;
20 }

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 void show(int array[], int len)
 4 {
 5     for(int i = 0; i < len ;i++)
 6     {
 7         cout << array[i]++ << " , ";
 8     }
 9     cout << endl;
10 }
11 void show1(const int array[], int len)//当我们不希望数组内容在函数体里面被修改的时候，我们可以对数组参数加const,变成一个常量
12 {
13     for(int i = 0; i < len ;i++)
14     {
15         //报错
16         //cout << array[i]++ << " , ";
17     }
18     cout << endl;
19 }
20 void show2(const int* begin,const int* end)//使用数组区间的函数
21 {
22      for(const int* ptr = begin; ptr <= end; ptr++){
23         cout <<*ptr << ",";
24      }
25 }
26 
27 int main()
28 {
29     int array[5] = {1,2,3,4,5};
30     int array1[5] = {1,2,3,4,5};
31     show(array,5);//1 , 2 , 3 , 4 , 5 ,
32     show(array,5);//2 , 3 , 4 , 5 , 6 ,
33     const int* ptr_begin = array;
34     show2(ptr_begin, ptr_begin - 1 + sizeof(array)/sizeof(int));
35     return 0;
36 }

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 void show(double (*arr)[5],int len){//二维数组做参数，行数大小要做参数传入
 4    for(int i = 0; i < len; i++)
 5    {
 6        for(int j = 0; j < 5; j++){
 7         cout << arr[i][j] << " || " << *(*(arr + i)+j) << " , " ;
 8        }
 9        cout <<endl;
10    }
11 }
12 int main()
13 {
14     double  array[2][5] = {
15         { 1, 2, 3, 4, 5},
16         { 1.1, 2.1, 33, 3.2,1.9}
17     };
18     show(array,2);
19     return 0;
20 }

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 int isZero = 0;
 4 double add(double a, double b)
 5 {
 6     return  a + b;
 7 }
 8 double subtraction(double a,double b)
 9 {
10     return a - b;
11 }
12 double mul(double a, double b)
13 {
14     return a * b;
15 }
16 double division(double a, double b)
17 {
18     if(b == 0){
19         cout << "分母不可为0";
20         isZero = 1;
21         return 0;
22     }else{
23         return a/b;
24     }
25 }
26 void print(double (*ptr)(double a,double b),double c, double d)//把函数指针做为参数传入
27 {
28     double c1=ptr(c, d);
29     if(isZero == 0){
30             cout << c1;
31     }else{
32       isZero = 0;
33     }
34 }
35 int main()
36 {
37     double a, b;
38     char ch = ‘ ‘;
39     int flag = 0;
40     double (*ptr)(double a, double b);
41     while(true){
42     cout << "-----请输入要计算的两个数------"  << endl;
43     cin >> a >> b;
44     cout << "请输入要执行何种计算（+,-,*,/）" << endl;
45     cin >> ch;
46     switch(ch)
47     {
48 
49         case ‘+‘: ptr = add; break;//函数指针作为各个函数的载体执行相应的运算，即该指针指向指定函数所在内存首地址
50         case ‘-‘: ptr = subtraction; break;
51         case ‘*‘: ptr = mul; break;
52         case ‘/‘: ptr = division; break;
53         default: cout << "输入错误,重新开始"  << endl; flag = 1;
54     }
55     if(flag == 1) { flag = 0;continue;};
56     cout << "结果是：";
57     print(ptr,a,b);
58     cout << endl;
59     cout << "是否跳出循环（y/n）" << endl;
60     char ch1 = ‘ ‘;
61     while(cin >> ch1)
62     {
63         if(ch1 == ‘y‘){
64             break;
65         }else if(ch1 == ‘n‘){
66             break;
67         }else{
68            cout << "请输入y or n" << endl;
69         }
70     }
71     if(ch1 == ‘n‘)  continue;
72     else  break;
73  }
74     return 0;
75 }