题解 | KiKi判断上三角矩阵

#include <stdio.h>

int main() {
    int n;
    scanf("%d", &n);
    int arr[n][n];

    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            scanf("%d", &arr[i][j]);
        }
    }

    //判断主对角线下三角元素是否全为0，为0的话count+1
    int count = 0;
    for (int i = 1; i < n; i++) {
        for (int j = 0; j < i; j++) {
            if (arr[i][j] == 0) {
                count++;
            }
        }
    }

    //将count的值与主对角线下三角元素个数对比
    if (count == n * (n - 1) / 2) {
        printf("YES");
    } else {
        printf("NO");
    }
    return 0;
}