How to Remove Duplicates in a List in C++ - Step by Step Examples

How to Remove Duplicates in a List in C++ ?

Answer

To remove duplicates in a list in C++ using std::list, you can use the unique method followed by the erase method.


✐ Examples

1 Remove Duplicates from Integer List

In this example,

  1. We create a list named numbers with integer values.
  2. We call the sort method on the list to ensure duplicates are adjacent.
  3. We call the unique method on the list to remove consecutive duplicate elements.
  4. We call the erase method to remove the duplicate elements.
  5. Finally, we print the list without duplicates to standard output.

C++ Program

#include <iostream>
#include <list>
#include <algorithm>
using namespace std;

int main() {
    list<int> numbers = {1, 2, 2, 3, 4, 4, 5};
    numbers.sort();
    numbers.unique();
    for (auto num : numbers) {
        cout << num << " ";
    }
    return 0;
}

Output

1 2 3 4 5

2 Remove Duplicates from String List

In this example,

  1. We create a list named words with string values.
  2. We call the sort method on the list to ensure duplicates are adjacent.
  3. We call the unique method on the list to remove consecutive duplicate elements.
  4. We call the erase method to remove the duplicate elements.
  5. Finally, we print the list without duplicates to standard output.

C++ Program

#include <iostream>
#include <list>
#include <algorithm>
using namespace std;

int main() {
    list<string> words = {"apple", "banana", "cherry", "apple", "banana"};
    words.sort();
    words.unique();
    for (auto word : words) {
        cout << word << " ";
    }
    return 0;
}

Output

apple banana cherry

Summary

In this tutorial, we learned How to Remove Duplicates in a List in C++ language with well detailed examples.


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