# 896. Monotonic Array 单调数列

@TOC

## # 题目描述

An array is monotonic if it is either monotone increasing or monotone decreasing.

An array `A` is monotone increasing if for all `i <= j`, `A[i] <= A[j]`. An array `A` is monotone decreasing if for all `i <= j`, `A[i] >= A[j]`.

Return `true` if and only if the given array `A` is monotonic.

Example 1:

``````Input: [1,2,2,3]
Output: true
``````

Example 2:

``````Input: [6,5,4,4]
Output: true
``````

Example 3:

``````Input: [1,3,2]
Output: false
``````

Example 4:

``````Input: [1,2,4,5]
Output: true
``````

Example 5:

``````Input: [1,1,1]
Output: true
``````

Note:

• 1 <= A.length <= 50000
• -100000 <= A[i] <= 100000

## # 解题方法

``````class Solution(object):
def isMonotonic(self, A):
"""
:type A: List[int]
:rtype: bool
"""
return self.isIncrease(A) or self.isDecrease(A)

def isIncrease(self, A):
return all(A[i] - A[i+1] >= 0 for i in range(len(A) - 1))

def isDecrease(self, A):
return all(A[i] - A[i+1] <= 0 for i in range(len(A) - 1))
``````

## # 日期

2018 年 9 月 3 日 —— 新学期开学第一天！ 2018 年 11 月 ９ 日 —— 睡眠可以2018 年 11 月 ９ 日 —— 睡眠可以