替代排序

给定一个整数数组，以第一个元素为第一个最大值而第二个元素为第一个最小值的方式打印该数组，依此类推。
例子 ：

Input : arr[] = {7, 1, 2, 3, 4, 5, 6}
Output : 7 1 6 2 5 3 4

Input : arr[] = {1, 6, 9, 4, 3, 7, 8, 2}
Output : 9 1 8 2 7 3 6 4

一个简单的解决方案是先打印最大元素，然后再打印最小值，然后再打印第二个最大值，依此类推。该方法的时间复杂度为O(n ² )。
一个有效的解决方案包括以下步骤。
1)使用O(n Log n)算法对输入数组进行排序。
2)在排序数组中，我们维护两个指针，一个从头开始，一个从头结束。我们也可以打印由两个指针指向的元素，并将它们彼此相对移动。

C++

// C++ program to print an array in alternate
// sorted manner.
#include 
using namespace std;
 
// Function to print alternate sorted values
void alternateSort(int arr[], int n)
{
    // Sorting the array
    sort(arr, arr+n);
 
    // Printing the last element of array
    // first and then first element and then
    // second last element and then second
    // element and so on.
    int i = 0, j = n-1;
    while (i < j) {
        cout << arr[j--] << " ";
        cout << arr[i++] << " ";
    }
 
    // If the total element in array is odd
    // then print the last middle element.
    if (n % 2 != 0)
        cout << arr[i];
}
 
// Driver code
int main()
{
    int arr[] = {1, 12, 4, 6, 7, 10};
    int n = sizeof(arr)/sizeof(arr[0]);
    alternateSort(arr, n);
    return 0;
}

Java

// Java program to print an array in alternate
// sorted manner
import java.io.*;
import java.util.Arrays;
  
class AlternativeString
{
    // Function to print alternate sorted values
    static void alternateSort(int arr[], int n)
    {
        Arrays.sort(arr);
 
        // Printing the last element of array
        // first and then first element and then
        // second last element and then second
        // element and so on.
        int i = 0, j = n-1;
        while (i < j) {
            System.out.print(arr[j--] + " ");
            System.out.print(arr[i++] + " ");
        }
      
        // If the total element in array is odd
        // then print the last middle element.
        if (n % 2 != 0)
            System.out.print(arr[i]);
    }
 
    /* Driver program to test above functions */
    public static void main (String[] args)
    {
        int arr[] = {1, 12, 4, 6, 7, 10};
        int n = arr.length;
        alternateSort(arr, n);
    }
}
/*This code is contributed by Prakriti Gupta*/

Python3

# Python 3 program to print an array
# in alternate sorted manner.
 
# Function to print alternate sorted
# values
def alternateSort(arr, n):
 
    # Sorting the array
    arr.sort()
 
    # Printing the last element of array
    # first and then first element and then
    # second last element and then second
    # element and so on.
    i = 0
    j = n-1
     
    while (i < j):
     
        print(arr[j], end =" ")
        j-= 1
        print(arr[i], end =" ")
        i+= 1
 
    # If the total element in array is odd
    # then print the last middle element.
    if (n % 2 != 0):
        print(arr[i])
 
 
# Driver code
arr = [1, 12, 4, 6, 7, 10]
n = len(arr)
 
alternateSort(arr, n)
 
# This code is contributed by
# Smitha Dinesh Semwal

C#

// C# program to print an array in alternate
// sorted manner
using System;
 
class AlternativeString {
     
    // Function to print alternate sorted values
    static void alternateSort(int[] arr, int n)
    {
        Array.Sort(arr);
 
        // Printing the last element of array
        // first and then first element and then
        // second last element and then second
        // element and so on.
        int i = 0, j = n - 1;
        while (i < j) {
            Console.Write(arr[j--] + " ");
            Console.Write(arr[i++] + " ");
        }
 
        // If the total element in array is odd
        // then print the last middle element.
        if (n % 2 != 0)
            Console.WriteLine(arr[i]);
    }
 
    /* Driver program to test above functions */
    public static void Main()
    {
        int[] arr = { 1, 12, 4, 6, 7, 10 };
        int n = arr.Length;
        alternateSort(arr, n);
    }
}
 
// This article is contributed by vt_m.

Javascript

      // JavaScript program to print an array in alternate
      // sorted manner.
 
      // Function to print alternate sorted values
      function alternateSort(arr, n)
      {
       
        // Sorting the array
        console.log(arr);
        arr.sort(function (a, b)
        {
          return a - b;
        });
        console.log(arr);
 
        // Printing the last element of array
        // first and then first element and then
        // second last element and then second
        // element and so on.
        var i = 0,
          j = n - 1;
        while (i < j)
        {
          document.write(arr[j--] + " ");
          document.write(arr[i++] + " ");
        }
 
        // If the total element in array is odd
        // then print the last middle element.
        if (n % 2 != 0) document.write(arr[i]);
      }
 
      // Driver code
      var arr = [1, 12, 4, 6, 7, 10];
      var n = arr.length;
      alternateSort(arr, n);
       
      // This code is contributed by rdtank.
    

输出 ：

12 1 10 4 7 6