p33

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LeetCode 33 Search in Rotated Sorted Array 题解

1.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.
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题意：

在一个被扭转的有序数组里查找一个数的坐标

2.解题思路:

二分搜索，先确定有序部分，在确定数字是否在此部分，如果在则进行二分搜索。

3.代码

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public class Solution {
    public int search(int[] nums, int target) {
        
		int s = 0;
		int e = nums.length - 1;
		while (s <= e) {
			int mid = (s + e) / 2;
			if (nums[mid] == target)
				return mid;

			if (nums[s] <= nums[mid]) {// 前部分全是有序的
				if (target < nums[mid] && target >= nums[s])
					e = mid - 1;
				else
					s = mid + 1;
			}

			if (nums[mid] <= nums[e]) {// 后部分全是有序的
				if (target > nums[mid] && target <= nums[e])
					s = mid + 1;
				else
					e = mid - 1;
			}
		}
		return -1;
    }
}

4.一些总结：