monotonic-array.py

# Time:  O(n)
# Space: O(1)

# 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

class Solution(object):
    def isMonotonic(self, A):
        """
        :type A: List[int]
        :rtype: bool
        """
        inc, dec = False, False
        for i in xrange(len(A)-1):
            if A[i] < A[i+1]:
                inc = True
            elif A[i] > A[i+1]:
                dec = True
        return not inc or not dec