【leetcode】1351. Count Negative Numbers in a Sorted Matrix

题目如下：

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

解题思路：送分题。

代码如下：

class Solution(object):
    def countNegatives(self, grid):
        """
        :type grid: List[List[int]]
        :rtype: int
        """
        res = 0
        for i in grid:
            for j in i:
                if j < 0:
                    res += 1
        return res