急急急！！！求教C语言问题！高手快来！！！

Question

Write a program that is able to compute some operations on an integer. The program writes the value of the integer and writes the following menu :

1. Add 1
2. Multiply by 2
3. Subtract 4
4. Quit

The programs ask the user to type a value between 1 and 4. If the user types a value from 1 to 3 the operation is computed, the integer is written and the menu is displayed again. If the user types 4, the program quits.

求高手解答感激不尽！！！

Answer 1

#include<iostream>
using namespace std;
int add(int);
int multiply(int);
int subtract(int);

int main(){
while(true){
int num;
cout<<"Please enter a value between 1 and 4\n";
cout<<"1. Add 1\n";
cout<<"2. Multiply by 2\n";
cout<<"3. Subtract 4\n";
cout<<"4. Quit\n";
char choice;
cin>>choice;
if(choice != '4')
cout<<"Please enter the num to be computed:\n";
cin>>num;
switch(choice){
case '1': cout<<add(num)<<endl;break;
case '2': cout<<multiply(num)<<endl;break;
case '3': cout<<subtract(num)<<endl;break;
case '4': exit(1);
default: cout<<"Wrong value!\n";
}
}
return 0;
}

int add(int num){
return num+1;
}
int multiply(int num){
return 2*num;
}
int subtract(int num){
return num-4;
}

Answer 2

别人做的还不是你的，天下没有捷径，一步一个脚印最稳妥。