leetcode 33 : Search in Rotated Sorted Array

原创于 2015-08-26 17:01:14 发布 · 342 阅读

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本文介绍了一种在已知旋转排序数组中查找特定元素的高效算法，通过逐步缩小搜索范围来实现目标值的快速定位。

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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.

代码

class Solution {
public:
    int search(vector<int>& nums, int target) {
        int low=0,high=nums.size()-1,middle;
        while(low<=high){
            middle=(low+high)/2;
            if(target == nums[middle]){     //先确定middle值是不是target
                return middle;
            }
            if(nums[low]<=nums[middle]){    //左边有序
                if(nums[low]<=target && target<nums[middle]){   //target在middle左边区域
                    high=middle-1;
                }else{
                    low=middle+1;
                }
            }else{                          //右边有序
                if(nums[middle]<target && target<=nums[high]){  //target在目标右边区域
                    low=middle+1;
                }else{
                    high=middle-1;
                }
            }

        }
        return -1;
    }
};