896. Monotonic Array

1. Question:

896. Monotonic Array

https://leetcode.com/problems/monotonic-array/

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

2. Solution:

class Solution:
    def isMonotonic(self, A):
        """
        :type A: List[int]
        :rtype: bool
        """
        if len(A) <= 1:
            return True

        size = len(A)
        begin = 1
        for i in range(1, size):
            if A[i - 1] == A[i]:
                continue
            if A[i - 1] < A[i]:
                increasing = True
            else:
                increasing = False
            begin = i
            break
        else:
            return True

        for i in range(begin, size):
            if increasing:
                if A[i - 1] > A[i]:
                    return False
            else:
                if A[i - 1] < A[i]:
                    return False

        return True

3. Complexity Analysis

Time Complexity : O(N)

Space Complexity: O(1)