LeetCode | Search in Rotated Sorted Array

题目

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.

分析

在二分查找的基础上，总结出旋转数组会对首尾指针的移动造成哪些改变，体现在在代码里即可。

代码

public class SearchInRotatedSortedArray {
	public int search(int[] A, int target) {
		if (A == null || A.length == 0) {
			return -1;
		}
		int low = 0;
		int high = A.length - 1;
		while (low <= high) {
			int mid = low + (high - low) / 2;
			if (target == A[mid]) {
				return mid;
			} else if (target < A[mid]) {
				if (A[mid] > A[high] && target < A[low]) {
					low = mid + 1;
				} else {
					high = mid - 1;
				}
			} else {
				if (A[mid] < A[low] && target > A[high]) {
					high = mid - 1;
				} else {
					low = mid + 1;
				}
			}
		}
		return -1;
	}
}