Find Minimum in Rotated Sorted Array

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.

分析：Seearch in rotated sorted array的变种，关键在于确定binary search的左右边界。代码如下：

class Solution {
public:
    int findMin(vector<int> &num) {
        int n = num.size();
        
        if(n == 1) return num[0];
        if(n == 2) return min(num[0], num[1]);
        if(num[0] < num[n-1])
            return num[0];
        
        int l = 0, r = n-1;
        
        while(l <= r){
            int mid = (l + r)/2;
            if(mid == n-1 && num[mid] < num[mid-1] || num[mid] < num[mid-1] && num[mid] < num[mid+1])
                return num[mid];
            if(num[mid] >= num[0])
                l = mid + 1;
            else r = mid - 1;
        }
    }
};