Remove duplicates from unsorted array

Given an unsorted array of integers, print the array after removing the duplicate elements from it. We need to print distinct array elements according to their first occurrence.

Examples:

Input: arr[] = { 1, 2, 5, 1, 7, 2, 4, 2}
Output: 1 2 5 7 4
Explanation: {1, 2} appear more than one time.

Input: arr[] = { 3, 3, 4, 1, 1}
Output: 3 4 1

Approach:

  • Take a Set
  • Insert all array element in the Set. Set does not allow duplicates and sets like LinkedHashSet maintains the order of insertion so it will remove duplicates and elements will be printed in the same order in which it is inserted.
  • Convert the formed set into array.
  • Print elements of Set.

Below is the implementation of the above approach:

C++

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// CPP program to remove duplicates
// from unsorted array
#include<bits/stdc++.h>
using namespace std;
  
// Function to remove duplicate from array
void removeDuplicates(int arr[], int n)
{
    set<int> s;
      
    // adding elements to LinkedHashSet
    for (int i = 0; i < n; i++)
        s.insert(arr[i]);
  
    // Print the elements of LinkedHashSet
    cout << "[ ";
    for(auto x:s)
    cout << x << " ";
    cout << "]";
}
  
// Driver code
int main()
{
    int arr[] = { 1, 2, 5, 1, 7, 2, 4, 2 };
    int n = sizeof(arr) / sizeof(arr[0]);
    removeDuplicates(arr, n);
}
  
// This code is contributed 
// by Surendra_Gangwar

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Java

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// Java program to remove duplicates
// from unsorted array
  
import java.util.*;
  
class GFG {
  
    // Function to remove duplicate from array
    public static void removeDuplicates(int[] arr)
    {
        LinkedHashSet<Integer> set
            = new LinkedHashSet<Integer>();
  
        // adding elements to LinkedHashSet
        for (int i = 0; i < arr.length; i++)
            set.add(arr[i]);
  
        // Print the elements of LinkedHashSet
        System.out.print(set);
    }
  
    // Driver code
    public static void main(String[] args)
    {
        int arr[] = { 1, 2, 5, 1, 7, 2, 4, 2 };
        removeDuplicates(arr);
    }
}

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Python3

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# Python3 program to remove duplcates
def removeDulipcates(arr):
    s = dict()
    d = []
  
    for i in arr:
        if i not in s.keys():
              
            # Adding elements to the dictionary
            d.append(i)
            s[i] = 1
      
    # Printing the dictionary
    print(d)
  
# Driver Code
arr = [1, 2, 5, 1, 7, 2, 4, 2]
removeDulipcates(arr)     
  
# This code is contributed
# by Mohit Kumar

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C#

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// C# program to remove duplicates
// from unsorted array
using System;
using System.Collections.Generic;
  
class GFG 
{
  
    // Function to remove duplicate from array
    public static void removeDuplicates(int[] arr)
    {
        HashSet<int> set = new HashSet<int>();
  
        // adding elements to LinkedHashSet
        for (int i = 0; i < arr.Length; i++)
            set.Add(arr[i]);
  
        // Print the elements of HashSet
        foreach(int item in set)
            Console.Write(item + ", ");
    }
  
    // Driver code
    public static void Main(String[] args)
    {
        int []arr = { 1, 2, 5, 1, 7, 2, 4, 2 };
        removeDuplicates(arr);
    }
}
  
// This code is contributed by 29AjayKumar

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Output:

[1, 2, 5, 7, 4]

Time Complexity: O(N)



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