LeetCode-Search in Rotated Sorted Array

Posted 2020-08-12 IncredibleThings

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.

 

 

public class Solution {
    public int search(int[] nums, int target) {
        if(nums==null || nums.length==0){
            return -1;
        }
        int low=0;
        int high=nums.length-1;
        
        while(low<=high){
            int mid=low+(high-low)/2;
            if(target<nums[mid]){
                if(nums[mid] < nums[high]){//right side is sorted
                    high=mid-1;//target must in the left side
                }
                else{
                    if(target<nums[low]){//target<nums[mid]&&target<nums[low]==>means,target cannot be in [low,mid] since this side is sorted
                        low=mid+1;
                    }
                    else{
                        high=mid-1;
                    }
                }
            }
            else if(target>nums[mid]){
                
                if(nums[mid]> nums[low]){//left side is sorted
                    low=mid+1;
                }
                else{
                    if(target>nums[high]){//target>nums[mid] && target>nums[high]==>means,target cannot be in [mid, high] since this side is sorted
                        high=mid-1;
                    }
                    else{
                        low=mid+1;
                    }
                }
            }
            else{
                return mid;
            }
        }
        return -1;
    }
}