Monotonic Array

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

这题是判断数组的单调性，但是有个要注意的是相等不影响之前的单调性，解法很简单直接：

class Solution {
public:
    bool isMonotonic(vector<int>& A) {
        int monotonic_style = 0;
        for (size_t i = 1; i < A.size(); i++) {
            if (A[i] > A[i - 1]) {
                if (monotonic_style == 0) {
                    monotonic_style = 1;
                } else if (monotonic_style != 1) {
                    return false;
                }
            } else if (A[i] < A[i - 1]) {
                if (monotonic_style == 0) {
                    monotonic_style = 2;
                } else if (monotonic_style != 2) {
                    return false;
                }
            }
        }
        return true;
    }
};