896. 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 Ais 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

思路：

1，判断是不是为1 ，是则直接返回true

2，设置递增、递减标志位，遍历时做比较，并使相应的标志位增加

3，判断标志位的值，若为a.length-1则为单调

#pragma once
#include <iostream>
#include<vector>

using namespace std;

class Solution {
public:
	bool isMonotonic(vector<int>& A) {
		//如果只有一位数，直接返回1
		if (A.size() == 1)
		{
			return true;
		}
		//两个标志，分别表示递增和递减的个数
		int increase = 0;
		int less = 0;



		for (int i = 0; i < A.size()-1; i++)
		{
			//满足递增，则递增标志位+1.
			if (A[i] >= A[i + 1])
			{
				increase++;
			}
			//满足递减，则递减标志位+1.
			if (A[i] <= A[i + 1])
			{
				less++;
			}
			
		}
		//只要递增或者递减标志位为A长度-1，则表示单调
		if (increase == A.size()-1 || less == A.size()-1)
		{
			return true;
		}
		else
		{
			return false;
		}
	}
};