Top K Frequent Elements

Medium 30 pts New · no attempts yet csharp

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Top K Frequent Elements — Uber interview prep · Arrays & Hashing

Classic interview problem #347.

Input (stdin)

Line 1: integers\nLine 2: k

Output (stdout)

k most frequent elements, space-separated, ascending tie-break

Your program must read from stdin and write the answer to stdout (no extra debug text).

Examples

Sample

Input

1 1 1 2 2 3
2

Output

1 2

Static hints

Input format: Line 1: integers\nLine 2: k
DSA Interview 150 — Arrays & Hashing
Problem #347
Frequently asked at Uber
Arrays & Hashing

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Your solution

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class Program
{
    static int[] Ria(string line = null)
    {
        line ??= Console.ReadLine();
        if (string.IsNullOrWhiteSpace(line)) return Array.Empty<int>();
        return line.Trim().Split(new[] { ' ', ',', '\t' }, StringSplitOptions.RemoveEmptyEntries)
            .Select(int.Parse).ToArray();
    }
    static string[] Rsa()
    {
        int n = int.Parse(Console.ReadLine());
        var arr = new string[n];
        for (int i = 0; i < n; i++) arr[i] = Console.ReadLine();
        return arr;
    }
    static void W(params object[] parts) => Console.WriteLine(string.Join(" ", parts));
    static void Wb(bool v) => Console.WriteLine(v ? "true" : "false");
    static void Wi(int v) => Console.WriteLine(v);
    static void Ws(string v) => Console.WriteLine(v);

static void Main()
    {
        // Read from stdin (see problem statement for format)
        // Line 1: integers\nLine 2: k

}
}

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Official solution

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class Program
{
    static int[] Ria(string line = null)
    {
        line ??= Console.ReadLine();
        if (string.IsNullOrWhiteSpace(line)) return Array.Empty<int>();
        return line.Trim().Split(new[] { ' ', ',', '\t' }, StringSplitOptions.RemoveEmptyEntries)
            .Select(int.Parse).ToArray();
    }
    static string[] Rsa()
    {
        int n = int.Parse(Console.ReadLine());
        var arr = new string[n];
        for (int i = 0; i < n; i++) arr[i] = Console.ReadLine();
        return arr;
    }
    static void W(params object[] parts) => Console.WriteLine(string.Join(" ", parts));
    static void Wb(bool v) => Console.WriteLine(v ? "true" : "false");
    static void Wi(int v) => Console.WriteLine(v);
    static void Ws(string v) => Console.WriteLine(v);

    static void Main()
    {
var nums = Ria();
int k = int.Parse(Console.ReadLine());
var freq = new Dictionary<int, int>();
foreach (var n in nums) freq[n] = freq.GetValueOrDefault(n) + 1;
var top = freq.OrderByDescending(kv => kv.Value).ThenBy(kv => kv.Key).Take(k).Select(kv => kv.Key);
W(string.Join(" ", top));
    }
}

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Explanation

Step 1 / 1

Uber interview context: Top K Frequent Elements is a Medium Arrays & Hashing problem — Use a hash map to trade space for O(1) lookups — classic at onsite rounds.

Use the animation above to step through each move before writing code.

Pattern: Arrays & Hashing

Read from stdin, write to stdout. Classic interview problem #347.

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