题解 | 上三角矩阵判定

#include <stdio.h>

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