Monotonic Array 单调数组

参考：
https://www.cnblogs.com/grandyang/p/10961560.html

#include <vector>
#include <stdlib.h>
#include <ostream>
#include <string>

using namespace std;
/**
 * @brief The Solution1 class
 * 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
 */

class Solution1{
public:
    bool isMonotonic(vector<int>& A){
        bool inc = true, dec = true;
        for(int i = 1; i < A.size(); ++i){
            inc &= (A[i-1] <= A[i]);
            dec &= (A[i-1] >= A[i]);
            if(!inc && !dec) return false;
        }
        return true;
    }
};

class Solution2{
public:
    bool isMonotonic(vector<int>&A){
        int inc = 1,dec = 1,n = A.size();
        for(int i = 1; i < n; ++i){
            inc += (A[i-1] <= A[i]);
            dec += (A[i-1] >= A[i]);
        }
        return (inc == n) || (dec == n);
    }
};