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Remove duplicates from a sorted array using STL in C++
  • Difficulty Level : Basic
  • Last Updated : 30 May, 2019

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

Examples:

Input: arr[] = {2, 2, 2, 2, 2}
Output: arr[] = {2}

Input: arr[] = {1, 2, 2, 3, 4, 4, 4, 5, 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 removeDuplicates(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;
  
    // 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, 2, 3, 4, 4, 4, 5, 5 };
  
    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 removeDuplicates()
    removeDuplicates(arr, n);
  
    return 0;
}
Output:
Before removing duplicates:
1 2 2 3 4 4 4 5 5 
After removing duplicates:
1, 2, 3, 4, 5,
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