leetcode117:search-rotated-sorted-array

题目描述

给出一个转动过的有序数组，你事先不知道该数组转动了多少
(例如,0 1 2 4 5 6 7可能变为4 5 6 7 0 1 2).
在数组中搜索给出的目标值，如果能在数组中找到，返回它的索引，否则返回-1。
假设数组中不存在重复项。

Suppose a sorted array is rotated at some pivot unknown to you beforehand.

(i.e.,0 1 2 4 5 6 7might become4 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.

示例1

输入

复制

[1],0

输出

复制

-1

class Solution {

public:

    int search(int A[], int n, int target) {

        if(A == nullptr||n==0)

            return -1;

        int left = 0;

        int right = n-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&&A[mid]>target)

                    right = mid-1;

                else

                    left = mid+1;

            }

            else{

                if(A[mid]<target&&A[right]>=target)

                    left = mid+1;

                else

                    right = mid-1;

            }

        }

        return -1;

    }

};