0
点赞
收藏
分享

微信扫一扫

[leetcode] 1351. Count Negative Numbers in a Sorted Matrix


Description

Given a m * n matrix grid which is sorted in non-increasing order both row-wise and column-wise.

Return the number of negative numbers in grid.

Example 1:

Input: grid = [[4,3,2,-1],[3,2,1,-1],[1,1,-1,-2],[-1,-1,-2,-3]]
Output: 8
Explanation: There are 8 negatives number in the matrix.

Example 2:

Input: grid = [[3,2],[1,0]]
Output: 0

Example 3:

Input: grid = [[1,-1],[-1,-1]]
Output: 3

Example 4:

Input: grid = [[-1]]
Output: 1

Constraints:

  • m == grid.length
  • n == grid[i].length
  • 1 <= m, n <= 100
  • -100 <= grid[i][j] <= 100

分析

题目的意思是:统计一个矩阵里面所有负数的个数,因为矩阵已经是有序了,负数集中在右方和下方,所以遍历的时候倒序遍历。

代码

class Solution:
def countNegatives(self, grid: List[List[int]]) -> int:
m=len(grid)
n=len(grid[0])
res=0
for i in range(m-1,-1,-1):
for j in range(n-1,-1,-1):
if(grid[i][j]<0):
res+=1
else:
break
return res


举报

相关推荐

0 条评论