Search in Rotated Sorted Array

Posted 2020-06-30

Suppose a sorted array is rotated at some pivot unknown to you beforehand.

(i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2).

You are given a target value to search. If found in the array return its index, otherwise return -1.

You may assume no duplicate exists in the array.

class Solution {
public:
    int search(vector<int>& nums, int target) {
     　　int lo=0,n=nums.size(),hi=n-1;
     
        while(lo<hi){
            int mid=(lo+hi)/2;
            if(nums[mid]>nums[hi]) lo=mid+1;
            else hi=mid;
        }
        int rot=lo;
        lo=0;hi=n-1;
        while(lo<=hi){
            int mid=(lo+hi)/2;
            int realmid=(mid+rot)%n;///？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？
            if(nums[realmid]==target)return realmid;
            if(nums[realmid]<target)lo=mid+1;
            else hi=mid-1;
        }
        return -1;
    }
};