1351. Count Negative Numbers in a Sorted Matrix

Problem Link

Description

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Given a m x 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

 

Constraints:

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

 

Follow up: Could you find an O(n + m) solution?

Solution

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Python3

class Solution:
    def countNegatives(self, grid: List[List[int]]) -> int:
        return sum(1 for i in range(len(grid)) for j in range(len(grid[0])) if grid[i][j] < 0)