c++ - 虽然循环不退出，即使它应该

Question

我写了一些代码，但 while 循环没有退出？

#include <iostream>

#define TriangleNumber(x) (x * (x + 1)) / 2

int main(int argc, char* argv[])
{
    int idx       = 0;
    int n_factors = 0;
    int triangle_num = 0;
    while (n_factors < 3)
    {
        int n_factors    = 0;
        triangle_num = TriangleNumber(idx);
        for (int i = 1; i <= triangle_num; i++)
        {
            if (triangle_num % i == 0)
            {
                n_factors++;
            }
        }
        idx++;
    }
    std::cout << "Number with greater than 3 factors = " << triangle_num;
    return 0;
}

期望在 idx = 3 和三角形编号 6 处退出。

Answer 1

您两次重新声明了完全相同的变量名称，因此 n_factors++ 指的是内部循环中的那个。从内部循环中删除 int，您的程序将输出

Number with greater than 3 factors = 6

工作代码:

#include <iostream>

#define TriangleNumber(x) (x * (x + 1)) / 2

int main(int argc, char* argv[])
{
    int idx       = 0;
    int n_factors = 0;
    int triangle_num = 0;
    while (n_factors < 3)
    {
        n_factors    = 0;
        triangle_num = TriangleNumber(idx);
        for (int i = 1; i <= triangle_num; i++)
        {
            if (triangle_num % i == 0)
            {
                n_factors++;
            }
        }
        idx++;
    }
    std::cout << "Number with greater than 3 factors = " << triangle_num;
    return 0;
}