Remove duplicates from an unsorted array using STL in C++

Given an unsorted array, the task is to remove the duplicate elements from the array using STL in C++

Examples:

Input: arr[] = {1, 2, 5, 1, 7, 2, 4, 2}
Output: arr[] = {1, 2, 4, 5, 7}
Input: arr[] = {1, 2, 4, 3, 5, 4, 4, 2, 5}
Output: arr[] = {1, 2, 3, 4, 5}

Approach:

The duplicates of the array can be removed using the unique() function provided in STL.

Below is the implementation of the above approach.

#include <bits/stdc++.h> 
using namespace std; 
  
// Function to remove duplicate elements 
void remDup(int arr[], int n) 
{ 
  
    // Initialise a vector 
    // to store the array values 
    // and an iterator 
    // to traverse this vector 
    vector<int> v(arr, arr + n); 
    vector<int>::iterator it; 
  
    // sorting vector 
    sort(v.begin(), v.end()); 
  
    // using unique() method 
    // to remove duplicates 
    it = unique(v.begin(), v.end()); 
  
    // resize the new vector 
    v.resize(distance(v.begin(), it)); 
  
    // Print the array with duplicates removed 
    cout << "\nAfter removing duplicates:\n"; 
    for (it = v.begin(); it != v.end(); ++it) 
        cout << *it << " "; 
    cout << '\n'; 
} 
  
// Driver code 
int main() 
{ 
    int arr[] = { 1, 2, 5, 1, 7, 2, 4, 2 }; 
  
    int n = sizeof(arr) / sizeof(arr[0]); 
  
    // Print array 
    cout << "\nBefore removing duplicates:\n"; 
    for (int i = 0; i < n; i++) 
        cout << arr[i] << " "; 
  
    // call remDup() 
    remDup(arr, n); 
  
    return 0; 
} 

Before removing duplicates:
1 2 5 1 7 2 4 2 
After removing duplicates:
1 2 4 5 7

Complexity:

Time complexity: O(nlog(n)) for sorting.

Space complexity: O(n) for storing the array into the vector.