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C++ Check if the Array Contains any Duplicates

Hello Everyone!

In this tutorial, we will learn how to check if the given Array contains any duplicate or not, in the C++ programming language.

This is achieved by first sorting the Array using the system defined sort() method, demonstrated below.

For better understanding, refer to the well-commented C++ code given below.


#include <iostream>
#include <bits/stdc++.h>

using namespace std;

//Program to return true if duplicate is found
bool containsDuplicate(int n[], int m)

    //flag to indicate the presence of duplicate
    int f = 0;

    //Sorting the array to check for duplicates
    sort(n, n + m);

    for (int i = 0; i < m - 1; i++)
        if (n[i] == n[i + 1])
            //if duplicate is found then set the flag to 1 and exit the loop
            f = 1;

    if (f == 1)
        return true;
        return false;

int main()
    cout << "\n\nWelcome to Studytonight :-)\n\n\n";
    cout << " ===== Program to check if any duplicates are present in the input array  ===== \n\n";

    int i, n1, n2;

    int a1[] = {2, 3, 1, 4, 5, 2, 8, 9};
    int a2[] = {2, 3, 1, 4, 5, 10, 8, 9};

    bool duplicate1 = false;

    bool duplicate2 = false;

    n1 = sizeof(a1) / sizeof(a1[0]);
    n2 = sizeof(a2) / sizeof(a2[0]);

    cout << "\n\nThe elements of the first input array are :\n\n";

    for (i = 0; i < n1; i++)
        cout << a1[i] << "  ";

    duplicate1 = containsDuplicate(a1, n1);

    if (duplicate1)
        cout << "\n\nThe first input array contains duplicate";
        cout << "\n\nThe first input array does not contain any duplicate";

    cout << "\n\n\n\nThe elements of the second input array are :\n\n";

    for (i = 0; i < n2; i++)
        cout << a2[i] << "  ";

    duplicate2 = containsDuplicate(a2, n2);

    if (duplicate2)
        cout << "\n\nThe second input array contains duplicate";
        cout << "\n\nThe second input array does not contain any duplicate";

    cout << "\n\n\n";

    return 0;


C++ duplicate check

We hope that this post helped you develop a better understanding of the concept of determining if the Array contains any duplicates and its implementation in C++. For any query, feel free to reach out to us via the comments section down below.

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About the author:
Nikita Pandey is a talented author and expert in programming languages such as C, C++, and Java. Her writing is informative, engaging, and offers practical insights and tips for programmers at all levels.