旋转数组搜索

问题：给定一个有序组的旋转和一个目标值，返回目标值在该数组的下标，如果没有，返回-1.假设该数组没有重复值。

依然使用二分查找法，OC算法实现：

//
//  SearchRotation.h
//  Algorithm
//
//  Created by han shuai on 2016/9/27.
//  Copyright © 2016年 han shuai. All rights reserved.
//
<p class="p1"><span class="s1">/**</span></p><p class="p1"><span class="s1"> 17</span></p><p class="p1"><span class="s1"> */</span></p>
#import <Foundation/Foundation.h>

@interface SearchRotation : NSObject

- (NSInteger)searchRotation:(NSArray *)dataArr target:(int)target;

@end

//
//  SearchRotation.m
//  Algorithm
//
//  Created by han shuai on 2016/9/27.
//  Copyright © 2016年 han shuai. All rights reserved.
//

#import "SearchRotation.h"

@implementation SearchRotation

- (NSInteger)searchRotation:(NSArray *)dataArr target:(int)target
{
    NSInteger left = 0;
    NSInteger right = dataArr.count-1;
    NSInteger mid = 0;
    
    while (left<right) {
        mid = (left+right)/2;
        if (dataArr[mid]>dataArr[left]) {
            //左半部分有序
            if (target == [dataArr[mid] intValue]) {
                return mid;
            }
            else if (target> [dataArr[left] intValue] && target<[dataArr[mid] intValue])
            {
                //目标数落在在有序列
                right = mid;
            }
            else if (target== [dataArr[left] intValue])
            {
                return left;
            }
            else
            {
                //目标数落在无序列
                left = mid;
            }
        }
        else
        {
            //右半部分有序
            if (target == [dataArr[mid] intValue]) {
                return mid;
            }
            else if (target > [dataArr[mid] intValue] && target < [dataArr[right] intValue])
            {
                //目标落在有序列
                left = mid;
            }
            else if (target == [dataArr[right] intValue])
            {
                return right;
            }
            else
            {
                //目标落在无序列
                right = mid;
            }
        }
    }
    
    return -1;
}

@end