Aquileo | Largest three distinct elements in an array

Given an array arr[], the task is to find the top three largest distinct integers present in the array.

Note: If there are less than three distinct elements in the array, then return the available distinct numbers in descending order.

Examples :

Input: arr[] = [10, 4, 3, 50, 23, 90]
Output: [90, 50, 23]
Input: arr[] = [10, 9, 9]
Output: [10, 9]
There are only two distinct elements
Input: arr[] = [10, 10, 10]
Output: [10]
There is only one distinct element

Try It Yourself

Table of Content

[Naive Approach] Three Traversals - O(n) Time and O(1) Space
[Efficient Approach] One Traversal - O(n) Time and O(1) Space

[Naive Approach] Three Traversals - O(n) Time and O(1) Space

First find the maximum in one pass, then find the maximum excluding it for the second largest, and again exclude both to get the third largest.

C++

#include <bits/stdc++.h>
using namespace std;

vector<int> get3largest(vector<int> &arr)
{
    int fst = INT_MIN, sec = INT_MIN, thd = INT_MIN;

    // Find the first largest element
    for (int x : arr)
    {
        if (x > fst)
            fst = x;
    }

    // Find the second largest element
    for (int x : arr)
    {
        if (x > sec && x != fst)
            sec = x;
    }

    // Find the third largest element
    for (int x : arr)
    {
        if (x > thd && x != fst && x != sec)
            thd = x;
    }

    vector<int> res;
    if (fst == INT_MIN) return res;
    res.push_back(fst);
    if (sec == INT_MIN) return res;
    res.push_back(sec);
    if (thd == INT_MIN) return res;
    res.push_back(thd);

    return res;
}

int main()
{
    vector<int> arr = {12, 13, 1, 10, 34, 1};
    vector<int> res = get3largest(arr);

    for (int x : res)
        cout << x << " ";
    cout << endl;

    return 0;
}

#include <stdio.h>
#include <limits.h>

void get3largest(int arr[], int n)
{
    int fst = INT_MIN, sec = INT_MIN, thd = INT_MIN;

    // Find the first largest element
    for (int i = 0; i < n; i++)
    {
        if (arr[i] > fst)
            fst = arr[i];
    }

    // Find the second largest element
    for (int i = 0; i < n; i++)
    {
        if (arr[i] > sec && arr[i] != fst)
            sec = arr[i];
    }

    // Find the third largest element
    for (int i = 0; i < n; i++)
    {
        if (arr[i] > thd && arr[i] != fst && arr[i] != sec)
            thd = arr[i];
    }

    if (fst != INT_MIN) printf("%d ", fst);
    if (sec != INT_MIN) printf("%d ", sec);
    if (thd != INT_MIN) printf("%d ", thd);

    printf("\n");
}

int main()
{
    int arr[] = {12, 13, 1, 10, 34, 1};
    int n = sizeof(arr) / sizeof(arr[0]);
    get3largest(arr, n);
    return 0;
}

Java

import java.util.ArrayList;

class GFG
{
    static ArrayList<Integer> get3largest(int[] arr)
    {
        int fst = Integer.MIN_VALUE;
        int sec = Integer.MIN_VALUE;
        int thd = Integer.MIN_VALUE;

        // Find the first largest element
        for (int x : arr)
        {
            if (x > fst)
                fst = x;
        }

        // Find the second largest element
        for (int x : arr)
        {
            if (x > sec && x != fst)
                sec = x;
        }

        // Find the third largest element
        for (int x : arr)
        {
            if (x > thd && x != fst && x != sec)
                thd = x;
        }

        ArrayList<Integer> res = new ArrayList<>();
        if (fst == Integer.MIN_VALUE) return res;
        res.add(fst);
        if (sec == Integer.MIN_VALUE) return res;
        res.add(sec);
        if (thd == Integer.MIN_VALUE) return res;
        res.add(thd);

        return res;
    }

    public static void main(String[] args)
    {
        int[] arr = {12, 13, 1, 10, 34, 1};
        ArrayList<Integer> res = get3largest(arr);

        for (int x : res)
            System.out.print(x + " ");
        System.out.println();
    }
}

Python

def get3largest(arr):
    fst = float('-inf')
    sec = float('-inf')
    thd = float('-inf')

    # Find the first largest element
    for x in arr:
        if x > fst:
            fst = x

    # Find the second largest element
    for x in arr:
        if x > sec and x != fst:
            sec = x

    # Find the third largest element
    for x in arr:
        if x > thd and x != fst and x != sec:
            thd = x

    res = []
    if fst == float('-inf'):
        return res
    res.append(fst)
    if sec == float('-inf'):
        return res
    res.append(sec)
    if thd == float('-inf'):
        return res
    res.append(thd)

    return res


if __name__ == "__main__":
    arr = [12, 13, 1, 10, 34, 1]
    res = get3largest(arr)
    print(" ".join(map(str, res)))

using System;
using System.Collections.Generic;

class GFG
{
    static List<int> get3largest(int[] arr)
    {
        int fst = int.MinValue;
        int sec = int.MinValue;
        int thd = int.MinValue;

        // Find the first largest element
        foreach (int x in arr)
        {
            if (x > fst)
                fst = x;
        }

        // Find the second largest element
        foreach (int x in arr)
        {
            if (x > sec && x != fst)
                sec = x;
        }

        // Find the third largest element
        foreach (int x in arr)
        {
            if (x > thd && x != fst && x != sec)
                thd = x;
        }

        List<int> res = new List<int>();
        if (fst == int.MinValue) return res;
        res.Add(fst);
        if (sec == int.MinValue) return res;
        res.Add(sec);
        if (thd == int.MinValue) return res;
        res.Add(thd);

        return res;
    }

    static void Main()
    {
        int[] arr = {12, 13, 1, 10, 34, 1};
        List<int> res = get3largest(arr);

        foreach (int x in res)
            Console.Write(x + " ");
        Console.WriteLine();
    }
}

JavaScript

function get3largest(arr)
{
    let fst = -Infinity;
    let sec = -Infinity;
    let thd = -Infinity;

    // Find the first largest element
    arr.forEach(x => {
        if (x > fst)
            fst = x;
    });

    // Find the second largest element
    arr.forEach(x => {
        if (x > sec && x !== fst)
            sec = x;
    });

    // Find the third largest element
    arr.forEach(x => {
        if (x > thd && x !== fst && x !== sec)
            thd = x;
    });

    let res = [];
    if (fst !== -Infinity) res.push(fst);
    if (sec !== -Infinity) res.push(sec);
    if (thd !== -Infinity) res.push(thd);

    return res;
}

let arr = [12, 13, 1, 10, 34, 1];
let res = get3largest(arr);
console.log(res.join(" "));

Output

34 13 12

[Efficient Approach] One Traversal - O(n) Time and O(1) Space

Keep track of the three largest values while scanning the array once, updating their positions whenever a bigger element is found, so the largest, second largest, and third largest are always maintained in order.

C++

#include <bits/stdc++.h>
using namespace std;

vector<int> get3largest(vector<int> &arr)
{
    int fst = INT_MIN, sec = INT_MIN, thd = INT_MIN;

    for (int x : arr)
    {
        // If current element is greater than fst
        if (x > fst)
        {
            thd = sec;
            sec = fst;
            fst = x;
        }

        // If x is between fst and sec
        else if (x > sec && x != fst)
        {
            thd = sec;
            sec = x;
        }

        // If x is between sec and thd
        else if (x > thd && x != sec && x != fst)
            thd = x;
    }

    vector<int> res = {};
    if (fst == INT_MIN)
        return res;
    res.push_back(fst);
    if (sec == INT_MIN)
        return res;
    res.push_back(sec);
    if (thd == INT_MIN)
        return res;
    res.push_back(thd);
    return res;
}

// Driver code
int main()
{
    vector<int> arr = {12, 13, 1, 10, 34, 1};

    vector<int> res = get3largest(arr);
    for (int x : res)
        cout << x << " ";
    cout << endl;

    return 0;
}

#include <stdio.h>
#include <limits.h>

void get3largest(int arr[], int n) {
    int fst = INT_MIN, sec = INT_MIN, thd = INT_MIN;

    for (int i = 0; i < n; i++) {
        int x = arr[i];
        // If current element is greater than fst
        if (x > fst) {
            thd = sec;
            sec = fst;
            fst = x;
        }
        // If x is between fst and sec
        else if (x > sec && x != fst) {
            thd = sec;
            sec = x;
        }
        // If x is between sec and thd
        else if (x > thd && x != sec && x != fst) {
            thd = x;
        }
    }

    if (fst != INT_MIN) printf("%d ", fst);
    if (sec != INT_MIN) printf("%d ", sec);
    if (thd != INT_MIN) printf("%d ", thd);

    printf("\n");
}

int main() {
    int arr[] = {12, 13, 1, 10, 34, 1};
    int n = sizeof(arr) / sizeof(arr[0]);
    get3largest(arr, n);
    return 0;
}