[二分搜索] leetcode 34 Find First and Last Position of Element in Sorted Array

Posted 2022-07-01 fish1996

problem:https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/

        经典二分搜索题。要点是改变low或high的时候把当前数字mid也包含进来，因为它也可能是结果。

class Solution 
public:
    vector<int> searchRange(vector<int>& nums, int target) 
        
        vector<int> res-1,-1;
        if(!nums.size()) return res;
        int low = 0;
        int high = nums.size() - 1;
        while(low < high)
        
            int mid = (low + high) / 2;
            
            if(target <= nums[mid])
            
                high = mid;
            
            else
            
                low = mid + 1;
            
        
        if(nums[low] == target) res[0] = low;
        
        low = 0;
        high = nums.size() - 1;
        while(low < high)
        
            int mid = (low + high + 1) / 2;
            
            if(target >= nums[mid])
            
                low = mid;
            
            else
            
                high = mid - 1;
            
            
        if(nums[low] == target) res[1] = low;
        return res;
    
;