在不使用额外空间的情况下将 2n 个整数随机播放为 a1-b1-a2-b2-a3-b3-..bn

我们有一个 {a0, a1, a2....., an, b0, b1, b2, .....bn} 形式的数组，我们的任务是使用 O(1) 空间重新排列下面给出的形式 -
{a0，b0，a1，b1，a2，b2……..an，bn}

例子：

Input : arr[] = {1, 3, 5, 7, 2, 4, 6, 8}
Output : {1, 2, 3, 4, 5, 6, 7, 8}

Input : arr[] = {11, 13, 15, 12, 14, 16}
Output : {11, 12, 13, 14, 15, 16}

我们已经讨论了两种方法——

https://www.geeksforgeeks.org/shuffle-2n-integers-format-a1-b1-a2-b2-a3-b3-bn-without-using-extra-space/
https://www.geeksforgeeks.org/shuffle-array-a1-b1-a2-b2-a3-b3-bn-without-using-extra-space/

正如我们所看到的，我们必须转换数组，所以必须有一个偶数大小的数组。要重新排列数组，我们将从数组的中间开始，每次我们将后半部分的 1 个元素向左移动到所需的位置.该算法将花费 O(n^2)。

算法-

1- Take the input array
2- If size is null or odd return
3- find the middle index of the array
4- While (midindex>0)
    set count = midindex and 
        swapindex = midindex
    while (count-->0){
      swap(swapindex+1, swapindedx)
      swapindex++
    }
    midindex--
5- End

在职的-

array- 1 3 5 7 2 4 6 8
1st Loop- 1 2 3 5 7 4 6 8
2nd Loop- 1 2 3 4 5 7 6 8
3rd loop- 1 2 3 4 5 6 7 8

C++

// C++ program to shuffle an array in
// the form of a1, b1, a2, b2,...
#include
using namespace std;
 
// function to rearrange the array
void rearrange(int arr[], int n)
{
 
    // if size is null or odd return because it
    // is not possible to rearrange
    if (arr == NULL || n % 2 == 1)
        return;
 
    // start from the middle index
    int currIdx = (n - 1) / 2;
 
    // each time we will set two elements from the
    // start to the valid position by swapping
    while (currIdx > 0)
    {
        int count = currIdx, swapIdx = currIdx;
     
        while (count-- > 0)
        {
            int temp = arr[swapIdx + 1];
            arr[swapIdx + 1] = arr[swapIdx];
            arr[swapIdx] = temp;
            swapIdx++;
        }
         
        currIdx--;
    }
}
 
// Driver Program
int main()
{
    int arr[] = {1, 3, 5, 2, 4, 6};
    int n = sizeof(arr) / sizeof(arr[0]);
    rearrange(arr, n);
    for (int i = 0; i < n; i++)
    cout << " " << arr[i];
 
}
 
// This code is contributed by Smitha Dinesh Semwal

Java

// Java program to shuffle an array in
// the form of a1, b1, a2, b2,...
import java.io.*;
 
class GFG {
 
  // function to rearrange the array
  public static void rearrange(int[] arr) {
 
    // if size is null or odd return because it
    // is not possible to rearrange
    if (arr == null || arr.length % 2 == 1)
      return;
 
    // start from the middle index
    int currIdx = (arr.length - 1) / 2;
 
    // each time we will set two elements from the
    // start to the valid position by swapping
    while (currIdx > 0) {
      int count = currIdx, swapIdx = currIdx;
 
      while (count-- > 0) {
        int temp = arr[swapIdx + 1];
        arr[swapIdx + 1] = arr[swapIdx];
        arr[swapIdx] = temp;
        swapIdx++;
      }
      currIdx--;
    }
  }
 
  public static void main(String[] args) {
    int arr[] = {1, 3, 5, 2, 4, 6};
    rearrange(arr);
    for (int i = 0; i < arr.length; i++)
      System.out.print(" " + arr[i]);
  }
}

Python3

# Python program to shuffle
# an array in the form
# of a1, b1, a2, b2,...
 
arr = [1, 3, 5, 2, 4, 6]
 
# function to
# rearrange the array
def rearrange(n) :
 
    global arr
     
    # if size is null or
    # odd return because
    # it is not possible
    # to rearrange
    if (n % 2 == 1) :
        return
 
    # start from the
    # middle index
    currIdx = int((n - 1) / 2)
 
    # each time we will set
    # two elements from the
    # start to the valid
    # position by swapping
    while (currIdx > 0) :
     
        count = currIdx
        swapIdx = currIdx
     
        while (count > 0) :
         
            temp = arr[swapIdx + 1]
            arr[swapIdx + 1] = arr[swapIdx]
            arr[swapIdx] = temp
            swapIdx = swapIdx + 1
            count = count - 1   
         
        currIdx = currIdx - 1
 
# Driver Code
n = len(arr)
rearrange(n)
for i in range(0, n) :
    print ("{} " . format(arr[i]),
                        end = "")
     
# This code is contributed by
# Manish Shaw(manishshaw1)

C#

// C# program to shuffle an array in
// the form of a1, b1, a2, b2,...
using System;
 
class GFG {
     
    // function to rearrange the array
    public static void rearrange(int[] arr)
    {
     
        // if size is null or odd return
        // because it is not possible to
        // rearrange
        if (arr == null || arr.Length % 2 == 1)
            return;
     
        // start from the middle index
        int currIdx = (arr.Length - 1) / 2;
     
        // each time we will set two elements
        // from the start to the valid position
        // by swapping
        while (currIdx > 0) {
            int count = currIdx, swapIdx = currIdx;
         
            while (count-- > 0) {
                int temp = arr[swapIdx + 1];
                arr[swapIdx + 1] = arr[swapIdx];
                arr[swapIdx] = temp;
                swapIdx++;
            }
             
            currIdx--;
        }
    }
     
    // Driver Program
    public static void Main() {
         
        int []arr = {1, 3, 5, 2, 4, 6};
         
        rearrange(arr);
         
        for (int i = 0; i < arr.Length; i++)
            Console.Write(" " + arr[i]);
    }
}
 
// This code is contributed by vt_m.

PHP

 0)
    {
        $count = $currIdx;
        $swapIdx = $currIdx;
     
        while ($count-- > 0)
        {
            $temp = $arr[$swapIdx + 1];
            $arr[$swapIdx + 1] = $arr[$swapIdx];
            $arr[$swapIdx] = $temp;
            $swapIdx++;
        }
         
        $currIdx--;
    }
}
 
// Driver Code
$arr = array(1, 3, 5, 2, 4, 6);
$n = count($arr);
rearrange($arr, $n);
for ($i = 0; $i < $n; $i++)
    echo ($arr[$i] . " ");
     
// This code is contributed by
// Manish Shaw(manishshaw1)
?>

Javascript

输出：

1 2 3 4 5 6