[LeetCode] Find Minimum in Rotated Sorted Array 二分搜索

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

 

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　　二分查找的变形，比较神奇的是数列可能没有旋转，查找前判断下数列旋转了没有便可以应对。

 

#include <iostream>

#include <vector>

using namespace std;



class Solution {

public:

    int findMin(vector<int> &num) {

        int n = num.size();

        if(n<2||num[0]<num[n-1]) return num[0];

        int lft=0,rgt=n-1,mid=n-1;

        while(lft+1<rgt){

            if(num[mid-1]>num[mid]) break;

            mid = (lft+ rgt)/2;

            cout<<lft<<" "<<mid<<" "<<rgt<<endl;

            if(num[lft]<num[mid])   lft=mid;

            else    rgt=mid;

            mid = rgt;

        }

        return num[mid];

    }

};



int main()

{

    vector<int> num{3,4,5,6,1,2};

    Solution sol;

    cout<<sol.findMin(num)<<endl;

    return 0;

}

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