Description
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.
题目链接：https://leetcode.com/problems/monotonic-array/description/
Difficulty: easy
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
分析
- 判断数组是否是递增或者递减的，定义判断量judge，judge=0初始化，judge=1递增，judge=-1递减，遍历数组；
- 如果judge=0：当前数大于前一个数，judge=1，如果当前数小于前一个数，judge=-1；
- 如果judge=1：如果当前数小于前一个数，返回False；
- 如果judge=-1：如果当前数大于前一个数，返回False；
- 遍历结束，返回True。
参考代码
class Solution:
def isMonotonic(self, A):
index = A[0]
judge=0
for i in range(1,len(A)):
if(judge==0):
if(A[i]>index):
judge=1
if(A[i]<index):
judge=-1
index=A[i]
elif(judge==1):
if(A[i]<index):
return False
index=A[i]
else:
if(A[i]>index):
return False
index=A[i]
return True
366 / 366 test cases passed.
Runtime: 160 ms