c++ - 需要额外的换行符

Question

#include <iostream>
using namespace std;
int main()
{
    int a;
    do
    {
        /* First reset the flag and then clean the buffer*/
        cin.ignore();
        cin.clear();
        /* Input the number from the user*/
        cout << "Enter number\n";
        cin >> a;
        /*Diplay appropiate error if the input was wrong*/
        if(cin.fail())
        {
            cout << "invalid input \n";
        }
        /*Display the number if the input was valid*/
        else
        {
            cout << "number entered is : " << a << endl;
        }
    }
    while(cin.fail());  //repeat until the input is correct
    return 0;
}

每次执行此程序时，我必须先输入一个新行，然后再执行cout<<"Enter number\n";。

其背后的原因是什么，可能的解决方案是什么。

注意:如果没有cin.ignore()，程序将进入无限循环

Answer 1

   cin.ignore();
   cin.clear();
   /* Input the number from the user*/
   cout << "Enter number\n";
   cin >> a;

至

   /* Input the number from the user*/
   cout << "Enter number\n";

   cin.clear();
   cin.ignore();
   cin >> a;