2026.9.11

74 搜索二维矩阵

class Solution:
    def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
        m,n=len(matrix),len(matrix[0])
        left=-1
        right=m*n
        while left+1<right:
            mid=(left+right)//2
            x=matrix[mid//n][mid%n]
            if target==x:return True
            if x<target:left=mid
            if x>target:right=mid
        return False

34 在排序数组中查找元素的第一个和最后一个位置

class Solution:
    def searchRange(self, nums: List[int], target: int) -> List[int]:
        def lower_bound(nums: List[int], target: int) -> List[int]:
            left,right=-1,len(nums)
            while left+1<right:
                mid=(left+right)//2
                x=nums[mid]
                if x<target:left=mid
                else:right=mid
            return right
        
        start=lower_bound(nums,target)
        if start==len(nums) or nums[start]!=target:return [-1,-1]
        end=lower_bound(nums,target+1)-1
        return [start,end]