class Solution:
    def isMonotonic(self, A: List[int]) -> bool:
        """ tc: O(N) sc: O(1)
        main idea: use dec,inc flags to keep track if each element follows monotonic rules 
        """
        dec = inc = True
        n = len(A)
        for i in range(1,n):
            inc &= A[i]>=A[i-1]
            dec &= A[i] <= A[i-1]
        return inc or dec