問題描述

#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;}

在程序中加斷點，發(fā)現(xiàn)運行到return l + 1處時報錯，報錯信息如下

在VSCODE中還會彈出一個窗口，提示源 源未知 不可用

請問問題出在哪里了？謝謝了

問題解答

通常win平臺非預期的sigtrap都是heap corruption。再看你的代碼，第十六行arr[j] = 1; 明顯有invalid write。所以vector arr(n, 0);的n應該改大一點，比如n+1。