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:
class Solution:
def countNegatives(self, grid: List[List[int]]) -> int:
m = len(grid)
n = len(grid[0])
ctr = 0
for i in range(m):
beg = 0
end = n - 1
while beg <= end:
mid = (beg + end) // 2
if beg == end:
if grid[i][beg] < 0:
ctr += (n - beg)
break
elif grid[i][mid] >= 0:
beg = mid + 1
else:
end = mid
return ctr
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