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Move all negative elements to end in order with extra space allowed

Given an unsorted array of both negative and positive integer. The task is place all negative element at the end of array without changing the order of positive element and negative element.

Examples:

Input : arr[] = {1, -1, 3, 2, -7, -5, 11, 6 }
Output : 1  3  2  11  6  -1  -7  -5 

Input : arr[] = {-5, 7, -3, -4, 9, 10, -1, 11}
Output : 7  9  10  11  -5  -3  -4  -1  




We have discussed different approaches to this problem in below post.

Rearrange positive and negative numbers with constant extra space

The problem becomes easier if we are allowed to use extra space. Idea is create an empty array (temp[]). First we store all positive element of given array and then we store all negative element of array in Temp[]. Finally we copy temp[] to original array.

Below is the implementation of above idea:

C/C++



// C++ program to Move All -ve Element At End
// Without changing order Of Array Element
#include<bits/stdc++.h>
using namespace std;
  
// Moves all -ve element to end of array in
// same order.
void segregateElements(int arr[], int n)
{
    // Create an empty array to store result
    int temp[n];
  
    // Traversal array and store +ve element in
    // temp array
    int j = 0; // index of temp
    for (int i = 0; i < n ; i++)
        if (arr[i] >= 0 )
            temp[j++] = arr[i];
  
    // If array contains all positive or all negative.
    if (j == n || j == 0)
        return;
  
    // Store -ve element in temp array
    for (int i = 0 ; i < n ; i++)
        if (arr[i] < 0)
            temp[j++] = arr[i];
  
    // Copy contents of temp[] to arr[]
    memcpy(arr, temp, sizeof(temp));
}
  
// Driver program
int main()
{
    int arr[] = {1 ,-1 ,-3 , -2, 7, 5, 11, 6 };
    int n = sizeof(arr)/sizeof(arr[0]);
  
    segregateElements(arr, n);
  
    for (int i = 0; i < n; i++)
       cout << arr[i] << " ";
  
    return 0;
}

Java

// Java program to Move All -ve Element At End
// Without changing order Of Array Element
import java.util.Arrays;
  
class GFG {
      
    // Moves all -ve element to end of array in
    // same order.
    static void segregateElements(int arr[], int n)
    {
          
        // Create an empty array to store result
        int temp[] = new int[n];
  
        // Traversal array and store +ve element in
        // temp array
        int j = 0; // index of temp
          
        for (int i = 0; i < n; i++)
            if (arr[i] >= 0)
                temp[j++] = arr[i];
  
        // If array contains all positive or all 
        // negative.
        if (j == n || j == 0)
            return;
  
        // Store -ve element in temp array
        for (int i = 0; i < n; i++)
            if (arr[i] < 0)
                temp[j++] = arr[i];
  
        // Copy contents of temp[] to arr[]
        for (int i = 0; i < n; i++)
            arr[i] = temp[i];
    }
      
    // Driver code
    public static void main(String arg[])
    {
        int arr[] = { 1, -1, -3, -2, 7, 5, 11, 6 };
        int n = arr.length;
  
        segregateElements(arr, n);
  
        for (int i = 0; i < n; i++)
            System.out.print(arr[i] + " ");
    }
}
  
// This code is contributed by Anant Agarwal.

Python

# Python program to Move All -ve Element At End
# Without changing order Of Array Element
   
# Moves all -ve element to end of array in
# same order.
def segregateElements(arr, n):
    # Create an empty array to store result
    temp = [0 for k in range(n)]
   
    # Traversal array and store +ve element in
    # temp array
    j = 0 # index of temp
    for i in range(n):
        if (arr[i] >= 0 ):
            temp[j] = arr[i]
            j +=1
   
    # If array contains all positive or all negative.
    if (j == n or j == 0):
        return
   
    # Store -ve element in temp array
    for i in range(n):
        if (arr[i] < 0):
            temp[j] = arr[i]
            j +=1
   
    # Copy contents of temp[] to arr[]
    for k in range(n):
        arr[k] = temp[k]
  
# Driver program
arr = [1 ,-1 ,-3 , -2, 7, 5, 11, 6 ]
n = len(arr)
  
segregateElements(arr, n);
   
for i in range(n):
    print arr[i],
  
# Contributed by Afzal aka Saan

C#

// C# program to Move All -ve Element At End
// Without changing order Of Array Element
using System;
  
class GFG {
  
    // Moves all -ve element to 
    // end of array in same order.
    static void segregateElements(int[] arr, int n)
    {
        // Create an empty array to store result
        int[] temp = new int[n];
  
        // Traversal array and store +ve element in
        // temp array
        int j = 0; // index of temp
  
        for (int i = 0; i < n; i++)
            if (arr[i] >= 0)
                temp[j++] = arr[i];
  
        // If array contains all positive or all
        // negative.
        if (j == n || j == 0)
            return;
  
        // Store -ve element in temp array
        for (int i = 0; i < n; i++)
            if (arr[i] < 0)
                temp[j++] = arr[i];
  
        // Copy contents of temp[] to arr[]
        for (int i = 0; i < n; i++)
            arr[i] = temp[i];
    }
  
    // Driver code
    public static void Main()
    {
        int[] arr = { 1, -1, -3, -2, 7, 5, 11, 6 };
        int n = arr.Length;
        segregateElements(arr, n);
  
        for (int i = 0; i < n; i++)
            Console.Write(arr[i] + " ");
    }
}
  
// This Code is contributed by vt_m.

PHP

<?php 
// PHP program to Move All -ve Element At End
// Without changing order Of Array Element
  
// Moves all -ve element to end of 
// array in same order.
function segregateElements(&$arr, $n)
{
    // Create an empty array to store result
    $temp = array(0, $n, NULL);
  
    // Traversal array and store +ve 
    // element in temp array
    $j = 0; // index of temp
    for ($i = 0; $i < $n ; $i++)
        if ($arr[$i] >= 0 )
            $temp[$j++] = $arr[$i];
  
    // If array contains all positive 
    // or all negative.
    if ($j == $n || $j == 0)
        return;
  
    // Store -ve element in temp array
    for ($i = 0 ; $i < $n ; $i++)
        if ($arr[$i] < 0)
            $temp[$j++] = $arr[$i];
  
    // Copy contents of temp[] to arr[]
    for($i = 0; $i < $n; $i++)
        $arr[$i] = $temp[$i];
}
  
// Driver Code
$arr = array(1 ,-1 ,-3 , -2, 7, 5, 11, 6 );
$n = sizeof($arr);
  
segregateElements($arr, $n);
  
for ($i = 0; $i < $n; $i++)
echo $arr[$i] ." ";
  
// This code is contributed 
// by ChitraNayal
?>


Output:

1 7 5 11 6 -1 -3 -2 

Time Complexity : O(n)
Auxiliary space : O(n)

Related Articles:
Rearrange positive and negative numbers with constant extra space
Rearrange positive and negative numbers in O(n) time and O(1) extra space

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.



This article is attributed to GeeksforGeeks.org

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