[Solved] 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.

Question

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?

Python Solution

class Solution:
    def countNegatives(self, grid: List[List[int]]) -> int:
        m=len(grid)
        n=len(grid[0])

        r,c,neg_count = 0,n-1,0

        while r<m and c>=0:
            if grid [r][c]<0:
                neg_count = neg_count + m-r
                c-=1
            else:
                r+=1
        return (neg_count)
Abhishek Sharma
Abhishek Sharma

Started my Data Science journey in my 2nd year of college and since then continuously into it because of the magical powers of ML and continuously doing projects in almost every domain of AI like ML, DL, CV, NLP.

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