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.

class Solution {
public:
    int findMin(vector<int> &num) {
        if (num.size() < 1)
        {
            return -1;
        }

        int left = 0; 
        int right = num.size() - 1;
        while (left < right-1)
        {
            int mid = left + (right-left)/2;
            if (num[mid] < num[left])
            {
                right = mid;
            }
            else    
            {
                if (num[mid] < num[right])
                {
                    right = mid;
                }
                else    
                {
                    left = mid;
                }
            }
        }

        if (num[left] < num[right])
        {
            return num[left];
        }

        return num[right];
    }
};