[LeetCode] 153. Find Minimum in Rotated Sorted Array_Medium

Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.

(i.e.,?[0,1,2,4,5,6,7]?might become ?[4,7,2]).

Find the minimum element.

You may assume no duplicate exists in the array.

Example 1:

Input: [3,2] 
Output: 1

Example 2:

Input: [4,2]
Output: 0

?

这个题目思路就是找到first number s.t <= nums[-1].利用Binary Search

T: O(lgn)

Code

class Solution:
    def minRotatedArray(self,nums):
        l,r,target = 0,len(nums) -1,nums[-1]
        if not nums: return -1
        while l + 1 < r:
            mid = l + (r - l)//2
            if nums[mid] <= target:
                r = mid
            else:
                l = mid
        return min(nums[l],nums[r])