Check if all array elements are distinct

Last Updated : 11 Jul, 2025

Given an array, check whether all elements in an array are distinct or not.

Examples:

Input : 1, 3, 2, 4
Output : Yes

Input : "Geeks", "for", "Geeks"
Output : No

Input : "All", "Not", "Equal"
Output : Yes

One simple solution is to use two nested loops. For every element, check if it repeats or not. If any element repeats, return True. If no element repeats, return false.

An efficient solution is to Hashing. We put all array elements in a HashSet. If size of HashSet remains same as array size, then we return true.

C++

// C++ program to check if all array 
// elements are distinct
#include <bits/stdc++.h>
using namespace std;

bool areDistinct(vector<int> arr)
{
    int n = arr.size();

    // Put all array elements in a map
    unordered_set<int> s;
    for (int i = 0; i < n; i++) {
        s.insert(arr[i]);
    }

    // If all elements are distinct, size of
    // set should be same array.
    return (s.size() == arr.size());
}

// Driver code
int main()
{
    std::vector<int> arr = { 1, 2, 3, 2 };

    if (areDistinct(arr)) {
        cout << "All Elements are Distinct";
    }
    else {
        cout << "Not all Elements are Distinct";
    }

    return 0;
}

Java

// Java program to check if all array elements are
// distinct or not.
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

public class DistinctElements {
    public static boolean areDistinct(Integer arr[])
    {
        // Put all array elements in a HashSet
        Set<Integer> s = 
           new HashSet<Integer>(Arrays.asList(arr));

        // If all elements are distinct, size of
        // HashSet should be same array.
        return (s.size() == arr.length);
    }

    // Driver code
    public static void main(String[] args)
    {
        Integer[] arr = { 1, 2, 3, 2 };
        if (areDistinct(arr))
            System.out.println("All Elements are Distinct");
        else
            System.out.println("Not all Elements are Distinct");
    }
}

Python3

# Python3 program to check if all array 
# elements are distinct
def areDistinct(arr) :

    n = len(arr)

    # Put all array elements in a map
    s = set()
    for i in range(0, n): 
        s.add(arr[i])
    
    # If all elements are distinct, 
    # size of set should be same array.
    return (len(s) == len(arr))

# Driver code
arr = [ 1, 2, 3, 2 ]

if (areDistinct(arr)): 
    print("All Elements are Distinct")

else : 
    print("Not all Elements are Distinct")

# This code is contributed by ihritik

// C# program to check if all array elements are
// distinct or not.
using System;
using System.Collections.Generic;

public class DistinctElements 
{
    public static bool areDistinct(int []arr)
    {
        // Put all array elements in a HashSet
        HashSet<int> s = new HashSet<int>(arr);

        // If all elements are distinct, size of
        // HashSet should be same array.
        return (s.Count == arr.Length);
    }

    // Driver code
    public static void Main(String[] args)
    {
        int[] arr = { 1, 2, 3, 2 };
        if (areDistinct(arr))
            Console.WriteLine("All Elements are Distinct");
        else
            Console.WriteLine("Not all Elements are Distinct");
    }
}

// This code has been contributed by 29AjayKumar

JavaScript

<script>
// Javascript program to check if all array
// elements are distinct
function areDistinct(arr)
{
    let n = arr.length;

    // Put all array elements in a map
    let s = new Set();
    for (let i = 0; i < n; i++) {
        s.add(arr[i]);
    }

    // If all elements are distinct, size of
    // set should be same array.
    return (s.size == arr.length);
}

// Driver code
    let arr = [ 1, 2, 3, 2 ];

    if (areDistinct(arr)) {
        document.write("All Elements are Distinct");
    }
    else {
        document.write("Not all Elements are Distinct");
    }

// This code is contributed
// by _saurabh_jaiswal
</script>

Output

Not all Elements are Distinct

Time complexity: O(n) where n is the size of the given array
Auxiliary space: O(n)

Distinct adjacent elements in a binary array

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