检查数组是递增还是递减

给定N个元素的数组arr [] ，其中N≥2 ，任务是检查数组的类型是否为：

1. 越来越多。
2. 减少。
3. 先升后降。
4. 先降后升。

注意，给定的数组肯定是给定类型之一。

例子：

Input: arr[] = {1, 2, 3, 4, 5}
Output: Increasing

Input: arr[] = {1, 2, 4, 3}
Output: Increasing then decreasing

方法：必须满足以下条件：

1. 递增数组：前两个元素和后两个元素必须按递增顺序排列。
2. 递减数组：前两个元素和后两个元素必须按递减顺序排列。
3. 先增后减数组：前两个元素必须按升序排列，后两个元素必须按降序排列。
4. 先降后升数组：前两个元素必须按降序排列，后两个元素必须按升序排列。

下面是上述方法的实现：

C++

// C++ implementation of the approach
#include 
using namespace std;
  
// Function to check the type of the array
void checkType(int arr[], int n)
{
  
    // If the first two and the last two elements
    // of the array are in increasing order
    if (arr[0] <= arr[1] && arr[n - 2] <= arr[n - 1])
        cout << "Increasing";
  
    // If the first two and the last two elements
    // of the array are in decreasing order
    else if (arr[0] >= arr[1] && arr[n - 2] >= arr[n - 1])
        cout << "Decreasing";
  
    // If the first two elements of the array are in
    // increasing order and the last two elements
    // of the array are in decreasing order
    else if (arr[0] <= arr[1] && arr[n - 2] >= arr[n - 1])
        cout << "Increasing then decreasing";
  
    // If the first two elements of the array are in
    // decreasing order and the last two elements
    // of the array are in increasing order
    else
        cout << "Decreasing then increasing";
}
  
// Driver code
int main()
{
    int arr[] = { 1, 2, 3, 4 };
    int n = sizeof(arr) / sizeof(arr[0]);
  
    checkType(arr, n);
  
    return 0;
}

Java

// Java implementation of the approach 
import java.math.*;
  
class GFG
{
  
    // Function to check the type of the array 
    public static void checkType(int arr[], int n) 
    { 
      
        // If the first two and the last two elements 
        // of the array are in increasing order 
        if (arr[0] <= arr[1] && 
            arr[n - 2] <= arr[n - 1]) 
            System.out.println("Increasing"); 
      
        // If the first two and the last two elements 
        // of the array are in decreasing order 
        else if (arr[0] >= arr[1] && 
                 arr[n - 2] >= arr[n - 1]) 
            System.out.println("Decreasing"); 
      
        // If the first two elements of the array are in 
        // increasing order and the last two elements 
        // of the array are in decreasing order 
        else if (arr[0] <= arr[1] &&
                 arr[n - 2] >= arr[n - 1]) 
            System.out.println("Increasing then decreasing"); 
  
        // If the first two elements of the array are in 
        // decreasing order and the last two elements 
        // of the array are in increasing order 
        else
            System.out.println("Decreasing then increasing");
    }
          
  
    // Driver code 
    public static void main(String[] args) 
    { 
        int[] arr = new int[]{ 1, 2, 3, 4 };
          
        int n = arr.length;
  
        checkType(arr, n); 
    }
}
  
// This code is contributed by Naman_Garg

Python3

# Python3 implementation of the approach 
  
# Function to check the type of the array 
def checkType(arr, n): 
  
    # If the first two and the last two elements 
    # of the array are in increasing order 
    if (arr[0] <= arr[1] and 
        arr[n - 2] <= arr[n - 1]) :
        print("Increasing"); 
  
    # If the first two and the last two elements 
    # of the array are in decreasing order 
    elif (arr[0] >= arr[1] and 
          arr[n - 2] >= arr[n - 1]) :
        print("Decreasing"); 
  
    # If the first two elements of the array are in 
    # increasing order and the last two elements 
    # of the array are in decreasing order 
    elif (arr[0] <= arr[1] and 
          arr[n - 2] >= arr[n - 1]) : 
        print("Increasing then decreasing"); 
  
    # If the first two elements of the array are in 
    # decreasing order and the last two elements 
    # of the array are in increasing order 
    else :
        print("Decreasing then increasing"); 
  
# Driver code 
if __name__ == "__main__" : 
  
    arr = [ 1, 2, 3, 4 ]; 
    n = len(arr); 
  
    checkType(arr, n); 
  
# This code is contributed by AnkitRai01

C#

// C# implementation of the approach 
using System;
class GFG
{
      
    // Function to check the type of the array 
    public static void checkType(int []arr, int n) 
    { 
      
        // If the first two and the last two elements 
        // of the array are in increasing order 
        if (arr[0] <= arr[1] && 
            arr[n - 2] <= arr[n - 1]) 
            Console.Write("Increasing"); 
      
        // If the first two and the last two elements 
        // of the array are in decreasing order 
        else if (arr[0] >= arr[1] && 
                 arr[n - 2] >= arr[n - 1]) 
            Console.Write("Decreasing"); 
      
        // If the first two elements of the array are in 
        // increasing order and the last two elements 
        // of the array are in decreasing order 
        else if (arr[0] <= arr[1] &&
                 arr[n - 2] >= arr[n - 1]) 
            Console.Write("Increasing then decreasing"); 
  
        // If the first two elements of the array are in 
        // decreasing order and the last two elements 
        // of the array are in increasing order 
        else
            Console.Write("Decreasing then increasing");
    }
  
    // Driver code 
    static public void Main ()
    {
        int[] arr = new int[]{ 1, 2, 3, 4 };
          
        int n = arr.Length;
  
        checkType(arr, n); 
    }
}
  
// This code is contributed by ajit

输出：

Increasing