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