从成对增加的相邻数组元素中重复删除一个元素后，找到最后剩余的元素

给定一个由N个整数组成的数组arr [] ，任务是在反复选择成对的递增相邻元素(arr [i]，arr [i + 1])并删除其中的任何元素后，打印最后剩余的数组元素。一对。如果无法将数组缩小为单个元素，则打印“ Not不可能” 。

例子：

Input: arr[] = {3, 1, 2, 4}
Output: 4
Explanation:
Step 1: Choose a pair (1, 2) and remove 2 from it. Now the array becomes [3, 1, 4].
Step 2: Choose pair (1, 4) and remove 1 from it. Now the array becomes [3, 4].
Step 3: Choose pair (3, 4) and remove 3 from it. Now the array becomes [4].
Hence, the remaining element is 4.

Input: arr[] = {2, 3, 1}
Output: Not Possible

方法：可以通过观察以下事实来解决给定的问题：如果第一个数组元素小于最后一个数组元素，则可以通过执行给定的操作来删除它们之间的所有元素。因此，只需检查arr [0] 是否正确。如果发现为真，则打印第一个或最后一个数组元素。否则，打印-1 。

下面是上述方法的实现：

C++14

// C++ program for the above approach
#include 
using namespace std;
 
// Function to print the last remaining
// array element after after performing
// given operations
void canArrayBeReduced(int arr[], int N)
{
    // If size of the array is 1
    if (N == 1) {
        cout << arr[0];
        return;
    }
 
    // Check for the condition
    if (arr[0] < arr[N - 1]) {
        cout << arr[N - 1];
    }
 
    // If condition is not satisfied
    else
        cout << "Not Possible";
}
 
// Driver Code
int main()
{
    int arr[] = { 6, 5, 2, 4, 1, 3, 7 };
    int N = sizeof(arr) / sizeof(arr[0]);
 
    // Function Call
    canArrayBeReduced(arr, N);
 
    return 0;
}

Java

// Java program for the above approach
import java.io.*;
class GFG
{
 
  // Function to print the last remaining
  // array element after after performing
  // given operations
  static void canArrayBeReduced(int[] arr, int N)
  {
 
    // If size of the array is 1
    if (N == 1)
    {
      System.out.print(arr[0]);
      return;
    }
 
    // Check for the condition
    if (arr[0] < arr[N - 1])
    {
      System.out.print(arr[N - 1]);
    }
 
    // If condition is not satisfied
    else
      System.out.print("Not Possible");
  }
 
  // Driver Code
  public static void main(String[] args)
  {
    int[] arr = { 6, 5, 2, 4, 1, 3, 7 };
    int N = arr.length;
 
    // Function Call
    canArrayBeReduced(arr, N);
  }
}
 
// This code is contributed by Dharanendra L V.

Python3

# Python 3 program for the above approach
 
# Function to print the last remaining
# array element after after performing
# given operations
def canArrayBeReduced(arr,  N):
 
    # If size of the array is 1
    if (N == 1):
        print(arr[0])
        return
 
    # Check for the condition
    if (arr[0] < arr[N - 1]):
        print(arr[N - 1])
 
    # If condition is not satisfied
    else:
        print("Not Possible")
 
 
# Driver Code
if __name__ == "__main__":
 
    arr = [6, 5, 2, 4, 1, 3, 7]
    N = len(arr)
 
    # Function Call
    canArrayBeReduced(arr, N)
 
    # This code is contributed by chitranayal.

C#

// C# program for the above approach
using System;
 
public class GFG {
 
  // Function to print the last remaining
  // array element after after performing
  // given operations
  static void canArrayBeReduced(int[] arr, int N)
  {
 
    // If size of the array is 1
    if (N == 1)
    {
      Console.Write(arr[0]);
      return;
    }
 
    // Check for the condition
    if (arr[0] < arr[N - 1])
    {
      Console.Write(arr[N - 1]);
    }
 
    // If condition is not satisfied
    else
      Console.Write("Not Possible");
  }
 
  // Driver Code
  static public void Main()
  {
    int[] arr = { 6, 5, 2, 4, 1, 3, 7 };
    int N = arr.Length;
 
    // Function Call
    canArrayBeReduced(arr, N);
  }
}
 
// This code is contributed by Dharanendra L V.

Javascript

// JavaScript program for the above approach
 
// Function to print the last remaining
// array element after after performing
// given operations
function canArrayBeReduced(arr, N)
{
 
    // If size of the array is 1
    if (N == 1)
    {
        document.write(arr[0]);
        return;
    }
 
    // Check for the condition
    if (arr[0] < arr[N - 1])
    {
        document.write(arr[N - 1]);
    }
 
    // If condition is not satisfied
    else
        document.write("Not Possible");
}
 
// Driver Code
 
    let arr = [ 6, 5, 2, 4, 1, 3, 7 ];
    let N = arr.length;
 
    // Function Call
    canArrayBeReduced(arr, N);
 
// This code is contributed by Surbhi Tyagi.

输出：

7

时间复杂度： O(1)
辅助空间： O(1)