LeetCode-Monotonic Array

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Description:
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

题意：给定一个数组，判断这个数组是否是单调的，可以是递增或者递减，但不是严格的单调，及元素可以相等；

解法：因为我们不知道数组是符合递增还是递减的，所以我们需要遍历两次数组是否符合递增或者递减中的一种情况；需要注意的是，对于数组[1,1,1,1]来说，不仅符合递增而且符合递减；

class Solution {
    public boolean isMonotonic(int[] A) {
        if (A.length == 1) {
            return true;
        }
        int len = 1;
        while(len < A.length && A[len] >= A[len - 1]) {
            len++;
        }
        if (len == A.length) {
            return true;
        }
        len = 1;
        while(len < A.length && A[len] <= A[len - 1]) {
            len++;
        }
        if (len == A.length) {
            return true;
        }
        return false;
    }
}