• 描述

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 static int search(int[] arr, int key) {
        if(arr == null || arr.length == 0)
            return -1;
        int low = 0, high = arr.length;
        while(low != high) {
            int mid  = low + (high - low) / 2;
            if(arr[mid] == key)
                return mid;
            if(arr[low] <= arr[mid]) {
                if(key >= low && key < arr[mid]) {
                    high = mid;
                }
                else {
                    low = mid + 1;
                }
            }
            else {
                if(key > arr[mid] && key <= arr[high-1] ) {
                    low = mid + 1;
                }
                else {
                    high = mid;
                }
            }
        }
        return -1;
    }
}