标签：The fir this info target tco 一个 二分 targe
Description: Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:
Link: 74. Search a 2D Matrix
Examples:
Example 1:
Input: matrix = [[1,3,5,7],[10,11,16,20],[23,30,34,60]], target = 3 Output: true Example 2:
Input: matrix = [[1,3,5,7],[10,11,16,20],[23,30,34,60]], target = 13 Output: false
思路: 首先确定是在哪一行，然后在这一行二分查找。怎么锁定在哪一行呢？用每行的最大值---最右面一列，结合第一列来确定，如果target <= m行最后一个值，那么target可能在mid行，或者更上面的行，用mid行的最小值确认是否在mid行，如果在，终止循环，如果不在，r = mid - 1。如果target > m行最后一个值, l = mid + 1. 确定了在哪一行，在这个行中普通二分查找就可以。
class Solution(object): def searchMatrix(self, matrix, target): """ :type matrix: List[List[int]] :type target: int :rtype: bool """ if target < matrix[0][0] or target > matrix[-1][-1]: return False m, n = len(matrix), len(matrix[0]) l, r = 0, m-1 i = -1 while l <= r: mid = int((l+r)/2) if target <= matrix[mid][-1]: if target >= matrix[mid][0]: i = mid break else: r = mid - 1 else: l = mid + 1 if i == -1: return False l, r = 0, n-1 while l <= r: mid = int((l+r)/2) if target == matrix[i][mid]: return True elif target > matrix[i][mid]: l = mid + 1 else: r = mid - 1 return False
日期: 2021-04-10 渐入佳境啊
Leetcode 74. Search a 2D Matrix
标签：The fir this info target tco 一个 二分 targe
原文地址：https://www.cnblogs.com/wangyuxia/p/14643205.html
