Rearrange an array in order – smallest, largest, 2nd smallest, 2nd largest, ..
Given an array of integers, the task is to print the array in the order – smallest number, the Largest number, 2nd smallest number, 2nd largest number, 3rd smallest number, 3rd largest number, and so on…..
Examples:
Input : arr[] = [5, 8, 1, 4, 2, 9, 3, 7, 6]
Output :arr[] = {1, 9, 2, 8, 3, 7, 4, 6, 5}
Input : arr[] = [1, 2, 3, 4]
Output :arr[] = {1, 4, 2, 3}
A simple solution is to first find the smallest element and swap it with the first element. Then find the largest element, swap it with the second element, and so on. The time complexity of this solution is O(n2).
An efficient solution is to use sorting.
- Sort the elements of the array.
- Take two variables say i and j and point them to the first and last index of the array respectively.
- Now run a loop and store the elements in the array one by one by incrementing i and decrementing j.
Let’s take an array with input 5, 8, 1, 4, 2, 9, 3, 7, 6 and sort them so the array becomes 1, 2, 3, 4, 5, 6, 7, 8, 9. Now take two variables to say i and j and point them to the first and last index of the array respectively, run a loop, and store the value into a new array by incrementing I and decrementing j.get that the final result as 1 9 2 8 3 7 4 6 5.
The flowchart is as follows:
flowchart- rearrangearray
Implementation:
C++
#include <bits/stdc++.h>
using namespace std;
void rearrangeArray( int arr[], int n)
{
sort(arr, arr + n);
int tempArr[n];
int ArrIndex = 0;
for ( int i = 0, j = n - 1; i <= n / 2 || j > n / 2;
i++, j--) {
tempArr[ArrIndex] = arr[i];
ArrIndex++;
tempArr[ArrIndex] = arr[j];
ArrIndex++;
}
for ( int i = 0; i < n; i++)
arr[i] = tempArr[i];
}
int main()
{
int arr[] = { 5, 8, 1, 4, 2, 9, 3, 7, 6 };
int n = sizeof (arr) / sizeof (arr[0]);
rearrangeArray(arr, n);
for ( int i = 0; i < n; i++)
cout << arr[i] << " " ;
return 0;
}
|
Java
import java.util.Arrays;
public class GFG {
static void rearrangeArray( int arr[], int n)
{
Arrays.sort(arr);
int [] tempArr = new int [n];
int ArrIndex = 0 ;
for ( int i = 0 , j = n- 1 ; i <= n / 2 || j > n / 2 ;
i++, j--) {
if (ArrIndex < n)
{
tempArr[ArrIndex] = arr[i];
ArrIndex++;
}
if (ArrIndex < n)
{
tempArr[ArrIndex] = arr[j];
ArrIndex++;
}
}
for ( int i = 0 ; i < n; i++)
arr[i] = tempArr[i];
}
public static void main(String args[])
{
int arr[] = { 5 , 8 , 1 , 4 , 2 , 9 , 3 , 7 , 6 };
int n = arr.length;
rearrangeArray(arr, n);
for ( int i = 0 ; i < n; i++)
System.out.print(arr[i]+ " " );
}
}
|
Python3
def rearrangeArray(arr, n) :
arr.sort()
tempArr = [ 0 ] * (n + 1 )
ArrIndex = 0
i = 0
j = n - 1
while (i < = n / / 2 or j > n / / 2 ) :
tempArr[ArrIndex] = arr[i]
ArrIndex = ArrIndex + 1
tempArr[ArrIndex] = arr[j]
ArrIndex = ArrIndex + 1
i = i + 1
j = j - 1
for i in range ( 0 , n) :
arr[i] = tempArr[i]
arr = [ 5 , 8 , 1 , 4 , 2 , 9 , 3 , 7 , 6 ]
n = len (arr)
rearrangeArray(arr, n)
for i in range ( 0 , n) :
print ( arr[i], end = " " )
|
C#
using System;
public class GFG {
static void rearrangeArray( int []arr, int n)
{
Array.Sort(arr);
int []tempArr = new int [n];
int ArrIndex = 0;
for ( int i = 0, j = n-1; i <= n / 2
|| j > n / 2; i++, j--) {
if (ArrIndex < n)
{
tempArr[ArrIndex] = arr[i];
ArrIndex++;
}
if (ArrIndex < n)
{
tempArr[ArrIndex] = arr[j];
ArrIndex++;
}
}
for ( int i = 0; i < n; i++)
arr[i] = tempArr[i];
}
public static void Main(String []args)
{
int []arr = {5, 8, 1, 4, 2, 9, 3, 7, 6};
int n = arr.Length;
rearrangeArray(arr, n);
for ( int i = 0; i < n; i++)
Console.Write(arr[i] + " " );
}
}
|
PHP
<?php
function rearrangeArray( $arr , $n )
{
sort( $arr );
$tempArr = array ( $n );
$ArrIndex = 0;
for ( $i = 0, $j = $n - 1;
$i <= $n / 2 || $j > $n / 2;
$i ++, $j --)
{
$tempArr [ $ArrIndex ] = $arr [ $i ];
$ArrIndex ++;
$tempArr [ $ArrIndex ] = $arr [ $j ];
$ArrIndex ++;
}
for ( $i = 0; $i < $n ; $i ++)
$arr [ $i ] = $tempArr [ $i ];
for ( $i = 0; $i < $n ; $i ++)
echo $arr [ $i ] . " " ;
}
$arr = array (5, 8, 1, 4, 2,
9, 3, 7, 6 );
$n = count ( $arr ) ;
rearrangeArray( $arr , $n );
?>
|
Javascript
<script>
function rearrangeArray(arr, n)
{
arr.sort();
let tempArr = new Array(n);
let ArrIndex = 0;
for (let i = 0, j = n-1; i <= n / 2
|| j > n / 2; i++, j--) {
if (ArrIndex < n)
{
tempArr[ArrIndex] = arr[i];
ArrIndex++;
}
if (ArrIndex < n)
{
tempArr[ArrIndex] = arr[j];
ArrIndex++;
}
}
for (let i = 0; i < n; i++)
arr[i] = tempArr[i];
}
let arr =[5, 8, 1, 4, 2, 9, 3, 7, 6]
let n = arr.length;
rearrangeArray(arr, n);
for (let i = 0; i < n; i++)
document.write(arr[i] + " " );
</script>
|
Time Complexity: O(n log n),
Auxiliary Space: O(n), since n extra space has been taken.
Last Updated :
21 Aug, 2022
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