在C++上运行程序，如果正确的话，再次询问输入

Question

我刚刚进入编程。我正在开发一个程序，它可以告诉奇数和偶数的数字小于或等于用户的输入（对于输入> = 0）。如何使程序运行，如果值> = 0，并要求再次输入，如果值是0 <这里 是程序：

> #include <iostream> 
using namespace std; 
int main() { 
    cout << "Please enter only a positive value\n"; 
    // Get number from user 
    int input = 0; 
    cout << "Enter a number:\n"; 
    cin >> input; 
    int number = 1; 
    while (input >= 0 && number <= input) { 
     // Print some numbers 
     cout << "Here are some odd numbers:\n"; 
     while (number <= input) { 
      cout << number << endl; 
      number = number + 2; 
     } 
     // Print some numbers 
     cout << "Here are some even numbers:\n"; 
     int number2 = 0; 
     while (number2 <= input) { 
      cout << number2 << endl; 
      number2 = number2 + 2; 
     } 
    } 
    return 0; 
} 

Answer 1

正确的代码：

#include <iostream> 
using namespace std; 
int main() { 
    cout << "Please enter only a positive value\n"; 
    // Get number from user 
    int input = 0; 
    cout << "Enter a number:\n"; 
    cin >> input; 
    while (input < 0) { 
     cout << "Input is negative. Enter again: \n"; 
     cin >> input; 
    } 
    int number = 1; 
    while (input >= 0 && number <= input) { 
     // Print some numbers 
     cout << "Here are some odd numbers:\n"; 
     while (number <= input) { 
      cout << number << endl; 
      number = number + 2; 
     } 
     // Print some numbers 
     cout << "Here are some even numbers:\n"; 
     int number2 = 0; 
     while (number2 <= input) { 
      cout << number2 << endl; 
      number2 = number2 + 2; 
     } 
    } 
    return 0; 
} 

请注意，我说这个块：

while (input < 0) { 
    cout << "Input is negative. Enter again: \n"; 
    cin >> input; 
} 

处理负输入。

Answer 2

while (input < 0) 
{ 
    cout << "Enter a number:\n"; 
    cin >> input; 
    if (input < 0) 
     // Here you can print something to tell that input was not correct 
}