c语言sscanf函数的用法是什么
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2022-08-25
[leetcode] 1351. Count Negative Numbers in a Sorted Matrix
Description
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: 8Explanation: 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.lengthn == grid[i].length1 <= m, n <= 100-100 <= grid[i][j] <= 100
分析
题目的意思是:统计一个矩阵里面所有负数的个数,因为矩阵已经是有序了,负数集中在右方和下方,所以遍历的时候倒序遍历。
代码
class Solution: def countNegatives(self, grid: List[List[int]]) -> int: m=len(grid) n=len(grid[0]) res=0 for i in range(m-1,-1,-1): for j in range(n-1,-1,-1): if(grid[i][j]<0): res+=1 else: break return res
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