LeetCode 852 Peak Index in a Mountain Array 解题报告

题目要求

Let's call an array A a mountain if the following properties hold:

• A.length >= 3

• There exists some 0 < i < A.length - 1 such that A[0] < A[1] < ... A[i-1] < A[i] > A[i+1] > ... > A[A.length - 1]

Given an array that is definitely a mountain, return any i such that A[0] < A[1] < ... A[i-1] < A[i] > A[i+1] > ... > A[A.length - 1].

题目分析及思路

题目给出一个整数数组，满足数组长度大于等于3且存在一个元素，它前面的元素依次递增，后面的元素依次递减。要求返回该元素的的索引。遍历数组，当某元素大于后一个元素则该元素即为所求元素。

python代码​

class Solution:

def peakIndexInMountainArray(self, A):

"""

:type A: List[int]

:rtype: int

"""

l = len(A)

for i in range(1,l):

if A[i-1]>A[i]:

return i-1