题解 | 上三角矩阵判定
上三角矩阵判定
https://www.nowcoder.com/practice/f5a29bacfc514e5a935723857e1245e4
n=int(input())
b=[]
flag='YES'
for _ in range (n):
a=list(map(int,input().split()))
b.append(a)
for i in range (n):
for j in range (i):
if b[i][j]!=0:
flag='NO'
break
print(flag)
