c++ - 从文件读取导致无限循环的问题

Question

好的，我正在处理的这个程序似乎一切正常，只是有一个问题。这是代码

#include <iostream>
#include <fstream>

using namespace std;

/*
Function Name: CalculateBinary
CalculateBinary takes a number from the main function and finds its binary form.
*/

void CalculateBinary( long InputNum)
{   
    //Takes InputNum and divides it down to "1" or "0" so that it can be put in binary form.
    if ( InputNum != 1 && InputNum != 0)
        CalculateBinary(InputNum/2);

    // If the number has no remainder it outputs a "0". Otherwise it outputs a "1". 
    if (InputNum % 2 == 0)
        cout << "0";
    else
        cout << "1";
}


void main()
{
    // Where the current number will be stored
      long InputNum;

    //Opens the text file and inputs first number into InputNum. 
    ifstream fin("binin.txt");
    fin >> InputNum;

    // While Input number is not 0 the loop will continue to evaluate, getting a new number each time.
    while (InputNum >= 0)
    {
        if(InputNum > 1000000000)
            cout << "Number too large for this program ....";
        else
            CalculateBinary(InputNum);

        cout << endl;
        fin >> InputNum;        
    }
}

这是我正在阅读的文本文件

12
8764
 2147483648
2
-1

当我到达 8764 时，它只是一遍又一遍地读取这个数字。它忽略了 2147483648。我知道我可以通过将 InputNum 声明为 long long 来解决这个问题。但我想知道它为什么要这样做？

Answer 1

这是您编写的此类循环的常见问题。

正确且惯用的循环是这样的:

ifstream fin("binin.txt");
long InputNum;
while (fin >> InputNum && InputNum >= 0)
{
   //now construct the logic accordingly!
    if(InputNum > 1000000000)
         cout << "Number too large for this program ....";
    else
         CalculateBinary(InputNum);
    cout << endl;
}