Monotonic Array

看一个队列是不是单调队列, 就是递增or递减.

class Solution {
    public boolean isMonotonic(int[] A) {
        if(A == null)
            return true;
        if(A.length == 1)
            return true;
        boolean res = true;
        for(int i = 1; i < A.length; i++) {
            if(A[i] < A[i-1])
                res = false;
        }
        if(res)
            return res;
        res = true; // set to true again.
        for(int i = 1; i < A.length; i++) {
            if(A[i] > A[i-1])
                res = false;
        }
        return res;
    }
}