852. 山脉数组的峰顶索引

题目分析可知肯定是有山峰的，所以其实就是找到最大值的索引就可以了

一、顺序查找

class Solution:
    def peakIndexInMountainArray(self, A: List[int]) -> int:
        i = 0
        while A[i] <= A[i+1]:
            i+=1
        return i

二、二分查找

class Solution:
    def peakIndexInMountainArray(self, A: List[int]) -> int:
        low = 0
        high = len(A) - 1
        while low <= high:
            mid =  (low + high) // 2
            middle_num = A[mid]
            if middle_num > A[mid-1]  and middle_num > A[mid+1]:
                return mid
            if A[mid-1]<A[mid]<A[mid+1]:
                low = mid + 1
            else:
                high = mid - 1

1.//是向下取整的意思吧

三、

 return A.index(max(A))

Python自带的函数一般都会有内部的优化