#include <algorithm> #include <iostream> #include <cmath> #include <vector>  using namespace std; int countPrimes(int n) {     if (n <= 2)         return 0;     vector<int> arr(n, 0);     for (int i = 2; i <= sqrt(n); ++i)     {         if (!arr[i])             for (int j = i * i; j <= n; j += i)             {                 arr[j] = 1;              }     }     cout << arr[2] << endl;     int j = 0;     for (int i = 2; i <= n; ++i)     {         if (!arr[i])         {             arr[j++] = i;         }      }     cout << "j" << j << endl;     int l = 0, r = j - 1;     while (l <= r)     {         int m = (l + r) >> 1;         cout << m << endl;         cout << "arr[m]" << arr[m] << "n - 1" << n - 1 << endl;         if (arr[m] == n - 1)         {             l = r = m;             return l + 1;         }         else if (arr[m] < n - 1)         {             l = m + 1;         }         else             r = m - 1;         cout << "l = " << l << "r= " << r << endl;         cout << "m=" << m << endl;     }     cout << l << endl;     return 0; }  int main() {     cout << countPrimes(6) << endl;      return 0; }

在程序中加断点，发现运行到return l + 1处时报错，报错信息如下

在VSCODE中还会弹出一个窗口，提示源 源未知 不可用

请问问题出在哪里了？谢谢了