Move all negative numbers to beginning and positive to end with constant extra space

An array contains both positive and negative numbers in random order. Rearrange the array elements so that all negative numbers appear before all positive numbers.

Examples :

Input : -12, 11, -13, -5, 6, -7, 5, -3, -6
Output :-12 -13 -5 -7 -3 -6 11 6 5

Note :- Order of elements is not important here.



The idea is to simply apply partition process of quicksort.

C++

filter_none

edit
close

play_arrow

link
brightness_4
code

// A C++ program to put all negative
// numbers before positive numbers
#include <bits/stdc++.h>
using namespace std;
  
void rearrange(int arr[], int n)
{
    int j = 0;
    for (int i = 0; i < n; i++) {
        if (arr[i] < 0) {
            if (i != j)
                swap(arr[i], arr[j]);
            j++;
        }
    }
}
  
// A utility function to print an array
void printArray(int arr[], int n)
{
    for (int i = 0; i < n; i++)
        printf("%d ", arr[i]);
}
  
// Driver code
int main()
{
    int arr[] = { -1, 2, -3, 4, 5, 6, -7, 8, 9 };
    int n = sizeof(arr) / sizeof(arr[0]);
    rearrange(arr, n);
    printArray(arr, n);
    return 0;
}

chevron_right


Java

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java program to put all negative
// numbers before positive numbers
import java.io.*;
  
class GFG {
  
    static void rearrange(int arr[], int n)
    {
        int j = 0, temp;
        for (int i = 0; i < n; i++) {
            if (arr[i] < 0) {
                if (i != j) {
                    temp = arr[i];
                    arr[i] = arr[j];
                    arr[j] = temp;
                }
                j++;
            }
        }
    }
  
    // A utility function to print an array
    static void printArray(int arr[], int n)
    {
        for (int i = 0; i < n; i++)
            System.out.print(arr[i] + " ");
    }
  
    // Driver code
    public static void main(String args[])
    {
        int arr[] = { -1, 2, -3, 4, 5, 6, -7, 8, 9 };
        int n = arr.length;
  
        rearrange(arr, n);
        printArray(arr, n);
    }
}
  
// This code is contributed by Nikita Tiwari.

chevron_right


Python3

filter_none

edit
close

play_arrow

link
brightness_4
code

# A Python 3 program to put
# all negative numbers before
# positive numbers
  
def rearrange(arr, n ) :
  
    # Please refer partition() in 
    # below post
    # https://www.geeksforgeeks.org / quick-sort / j = 0
    j = 0 
    for i in range(0, n) :
        if (arr[i] < 0) :
            temp = arr[i]
            arr[i] = arr[j]
            arr[j]= temp
            j = j + 1
    print(arr)
  
# Driver code
arr = [-1, 2, -3, 4, 5, 6, -7, 8, 9]
n = len(arr)
rearrange(arr, n)
  
  
# This code is contributed by Nikita Tiwari.

chevron_right


C#

filter_none

edit
close

play_arrow

link
brightness_4
code

// C# program to put all negative
// numbers before positive numbers
using System;
  
class GFG {
    static void rearrange(int[] arr, int n)
    {
  
        int j = 0, temp;
        for (int i = 0; i < n; i++) {
            if (arr[i] < 0) {
                temp = arr[i];
                arr[i] = arr[j];
                arr[j] = temp;
                j++;
            }
        }
    }
  
    // A utility function to print an array
    static void printArray(int[] arr, int n)
    {
        for (int i = 0; i < n; i++)
            Console.Write(arr[i] + " ");
    }
  
    // Driver code
    public static void Main()
    {
        int[] arr = { -1, 2, -3, 4, 5, 6, -7, 8, 9 };
        int n = arr.Length;
  
        rearrange(arr, n);
        printArray(arr, n);
    }
}
  
// This code is contributed by nitin mittal.

chevron_right


PHP

filter_none

edit
close

play_arrow

link
brightness_4
code

<?php 
// A PHP program to put all negative
// numbers before positive numbers
  
function rearrange(&$arr, $n)
{
    $j = 0;
    for ($i = 0; $i < $n; $i++)
    {
        if ($arr[$i] < 0) 
        {
            if ($i != $j)
            {
                $temp = $arr[$i];
                $arr[$i] = $arr[$j];
                $arr[$j] = $temp;
            }
            $j++;
        }
    }
}
  
// A utility function to print an array
function printArray(&$arr, $n)
{
    for ($i = 0; $i < $n; $i++)
        echo $arr[$i]." ";
}
  
// Driver code
$arr = array(-1, 2, -3, 4, 5, 6, -7, 8, 9 );
$n = sizeof($arr);
rearrange($arr, $n);
printArray($arr, $n);
  
// This code is contributed by ChitraNayal
?>

chevron_right



Output:

 -1 -3 -7 4 5 6 2 8 9 

Time complexity: O(n)
Auxiliary Space: O(1)

The problem becomes difficult if we need to maintain order of elements. Please refer Rearrange positive and negative numbers with constant extra space for details.

This article is contributed by Apoorva. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@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.



My Personal Notes arrow_drop_up



Article Tags :
Practice Tags :


1


Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.