Find Minimum in Rotated Sorted Array【153】

Datetime:2016-08-23 01:23:23          Topic: LeetCode           Share

153. Find Minimum in Rotated Sorted Array

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Total Accepted:  73048 Total Submissions:  209952 Difficulty:  Medium

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 ).

Find the minimum element.

You may assume no duplicate exists in the array.

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Array   Binary Search
//思路首先:遍历一遍时间复杂度是O(N)
class Solution {
public:
    int findMin(vector<int>& nums) {
        int minum=nums[0];
        for(int i=1;i<nums.size();i++)
        {
            if(nums[i]<minum)
                minum=nums[i];
        }
        return minum;
    }
};
//思路首先:第二种方法还是直接遍历,
//按照题目所说数组应该是先上升,在下降,如果下降了,这个值就是最小值
class Solution {
public:
    int findMin(vector<int>& nums) {
        int minum=nums[0];
        for(int i=1;i<nums.size();i++)
        {
            if(nums[i-1]>nums[i])
               { 
                   minum=nums[i];
                   break;
               }
        }
        return minum;
    }
};
//思路首先:第三种方法,二分法
//
class Solution {
public:
    int findMin(vector<int>& nums) {
        if(nums.empty())
            return 0;
        if(nums.size() == 1)
            return nums[0];

        int low = 0, high = nums.size()-1;
        while(low < high && nums[low] > nums[high])
        {
            int mid = low + (high-low)/2;
            if(nums[mid] < nums[low])  
                high = mid;
            else if(nums[mid] == nums[low]) 
                return nums[high]; 
            else
                low = mid+1;
        }
        return nums[low];
    }
};




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