题解 | #KiKi判断上三角矩阵#

#include <stdio.h>

int main() {
    int n = 0;
    scanf("%d", &n);
    //int arr[n][n];
    int arr[10][10] = {0};
    int i = 0;
    int j = 0;
    int flag = 1;
    for (i = 0; i < n; i++) {
        for (j = 0; j < n; j++) {
            scanf("%d", &arr[i][j]);
        }
    }
    for (i = 0; i < n; i++) {
        for (j = 0; j < i; j++) {
            if(arr[i][j] !=0)
            {
                flag = 0;
                goto end;
            }
        }
    }
    end:
    if(flag==0)
        printf("NO\n");
    else 
        printf("YES\n");


    return 0;
}