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++

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// 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;
}

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Java














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// 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. 



















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Python3














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# 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. 



















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C#














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// 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. 



















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PHP














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<?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 


?> 



















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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.


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