Algorithm

[LeetCode 33] Search in Rotated Sorted Array [Java]

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2018-01-23

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01/23

1. Description

Suppose an array sorted in ascending order 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.

2. Example

4 5 6 7 0 1 2
given target 0, return 4
given target 6, return 2

3. Code


public class LeetCode0033 {

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

    public static void main(String[] args) {
        LeetCode0033 leetcode = new LeetCode0033();
        System.out.println(leetcode.search(new int[] { 4, 5, 6, 7, 0, 1, 2 }, 0));
    }
}

Array

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