leetcode 1351 - Count Negative Numbers in a Sorted Matrix

https://leetcode.com/problems/count-negative-numbers-in-a-sorted-matrix/

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

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class Solution {
public:
int countNegatives(vector<vector<int>>& grid) {
int row = grid.size(), col = grid[0].size();

int total = 0;

int r = row - 1, c = 0;

while (r >= 0 && c < col) {
if (grid[r][c] < 0) {
total += col - c;
r--;
} else {
c++;
}
}

return total;
}
};