README_EN.md

896. Monotonic Array

中文文档

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.

 

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. 1 <= A.length <= 50000
2. -100000 <= A[i] <= 100000

Solutions

Python3

class Solution:
    def isMonotonic(self, A: List[int]) -> bool:
        increase = decrease = True
        for i in range(1, len(A)):
            if not increase and not decrease:
                return False
            if A[i] < A[i - 1]:
                increase = False
            elif A[i] > A[i - 1]:
                decrease = False
        return increase or decrease

Java

class Solution {
    public boolean isMonotonic(int[] A) {
        boolean increase = true, decrease = true;
        for (int i = 1, n = A.length; i < n; ++i) {
            if (!increase && !decrease) return false;
            if (A[i] < A[i - 1]) decrease = false;
            else if (A[i] > A[i - 1]) increase = false;
        }
        return increase || decrease;
    }
}

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