Time Based Key-Value Store

Medium 30 pts New · no attempts yet csharp

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Time Based Key-Value Store — Uber interview prep · Binary Search

Classic interview problem #981.

Input (stdin)

Lines: SET key value timestamp | GET key timestamp

Output (stdout)

Value at timestamp

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

Examples

Sample

Input

SET foo bar 1
SET foo bar2 4
GET foo 3

Output

bar

Static hints

Input format: Lines: SET key value timestamp | GET key timestamp
DSA Interview 150 — Binary Search
Problem #981
Frequently asked at Uber
Binary Search

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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)
        // Lines: SET key value timestamp | GET key timestamp

}
}

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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 map = new Dictionary<string, List<(int t, string v)>>();
string queryKey = null; int queryTs = 0;
string line;
while ((line = Console.ReadLine()) != null) {
    if (line.StartsWith("SET ")) {
        var p = line.Split(' ');
        string k = p[1], v = p[2]; int t = int.Parse(p[3]);
        if (!map.ContainsKey(k)) map[k] = new List<(int, string)>();
        map[k].Add((t, v));
    } else if (line.StartsWith("GET ")) {
        var p = line.Split(' ');
        queryKey = p[1]; queryTs = int.Parse(p[2]);
    }
}
string ans = "";
if (map.ContainsKey(queryKey)) {
    foreach (var (t, v) in map[queryKey])
        if (t <= queryTs) ans = v;
}
Ws(ans);
    }
}

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Explanation

Step 1 / 1

Uber interview context: Time Based Key-Value Store is a Medium Binary Search problem — Binary search on index or on the answer (binary search on value).

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

Pattern: Binary Search

Read from stdin, write to stdout. Classic interview problem #981.

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