Search in Rotated Sorted Array

最新推荐文章于 2020-08-05 08:57:53 发布

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本文介绍了一种在旋转排序数组中查找目标值的高效算法。该算法利用二分查找的思想，在O(log n)的时间复杂度内完成搜索。文章提供了一个Java实现示例，详细解释了如何根据数组旋转特性调整搜索范围。

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[] A, int target) {
        if (A == null || A.length == 0) return -1;
        int left = 0;
        int right = A.length - 1;
        while (left <= right) {
            int mid = left + (right - left) / 2;
            if (A[mid] == target) {
                return mid;
            } 
            if (A[left] <= A[mid]) {
                if (A[left] <= target && target < A[mid]) {
                    right = mid - 1;
                } else {
                    left = mid + 1;
                }
            } else {
                if (A[mid] < target && target <= A[right]) {
                    left = mid + 1;
                } else {
                    right = mid - 1;
                }
            }
        }
        return -1;
    }
}