Extra output when writing to file using std::cout-CodePudding

I am trying to read data from a file in.txt, and after some computations, I am writing the output to out.txt

Why is there an extra 7 at the end of out.txt?

Contents of `Solution` class.

class Solution
{
public:
    int findComplement(int num)
    {
        int powerof2 = 2, temp = num;

        /*
        get number of bits corresponding to the number, and
        find the smallest power of 2 greater than the number.
        */
        while (temp >> 1)
        {
            temp >>= 1;
            powerof2 <<= 1;
        }

        // subtract the number from powerof2 -1
        return powerof2 - 1 - num;
    }
};

Contents of `main` function.

Assume all headers are included. findComplement flips bits of a number. For example, The integer 5 is "101" in binary and its complement is "010" which is the integer 2.

int main() {

#ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
#endif

    // helper variables
    Solution answer;
    int testcase;

    // read input file, compute answer, and write to output file
    while (std::cin) {
        std::cin >> testcase;
        std::cout << answer.findComplement(testcase) << "\n";
    }
    return 0;
}

Contents of `in.txt`

Contents of `out.txt`

CodePudding user response：

The reason there is an extra 7 is that your loop executes one too many times. You need to check std::cin after you've tried to read the input.

As is, you simply repeat the last test case.

Contents of Solution class.

Contents of main function.

Contents of in.txt

Contents of out.txt

Contents of `Solution` class.

Contents of `main` function.

Contents of `in.txt`

Contents of `out.txt`