LeetCode 33 Search in Rotated Sorted Array

题目

c++

二分

class Solution {
public:
    int search(vector<int>& nums, int target) {
        
        if(nums.size()==0)
            return -1;
        int start=0;
        int end = nums.size()-1;
        
        int ans=-1;
        while(start<end)
        {
            int mid = (start+end)/2;
            
            if(target < nums[mid])
            {
                if(target>=nums[start]&&nums[start]<nums[mid])
                {
                    end = mid-1;
                }
                else if(target<=nums[end]&&nums[end]<nums[mid])
                {
                    start = mid+1;
                }
                else
                    end=mid-1;
                
            }
            else if(target > nums[mid])
            {
                if(target>=nums[start]&&nums[start]>nums[mid])
                {
                    end = mid-1;
                }
                else if(target>=nums[end]&&nums[end]<nums[mid])
                {
                    start = mid+1;
                }
                else
                    start = mid+1;
            }
            else
            {
                ans=mid;
                break;
            }
        }
        
        if(ans!=-1)
            return ans;
        
        ans = start;
        if(nums[start]!=target)
            ans=-1;
        
        return ans;
    }
};