Given an array of integers, task is to print the array in the order – smallest number, 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, swap it with first element. Then find largest element, swap it with second element and so on. Time complexity of this solution is O(n2).
An efficient solution is to use sorting.
1. Sort the elements of array.
2. Take two variables say i and j and point them to the first and last index of the array respectively.
3. 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 become 1, 2, 3, 4, 5, 6, 7, 8, 9. Now take two variables say i and j and point them to the first and last index of the array respectively, run a loop and store value into new array by incrementing i and decrementing j. We get final result as 1 9 2 8 3 7 4 6 5.
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>
|
Output:
1 9 2 8 3 7 4 6 5
Time Complexity : O(n Log n)
Auxiliary Space : O(n)
This article is contributed by Ayush Saxena. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.