Remove duplicates from unsorted array using Set data structure

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

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

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++

// 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) 
{ 
    unordered_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 

Java

// 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); 
    } 
} 

Python3

# 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 

C#

// 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 

Output:

[ 4 7 5 1 2 ]

Time Complexity: O(N)

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My Personal Notes

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

C++

Java

Python3

C#

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