C# Dictionary Scenario-Based Coding Questions (M1 Mock Test)

Practice 20 interview-style scenarios focused on Dictionary<TKey, TValue>. Each question includes a starter boilerplate to help associates begin quickly.

1) Inventory Lookup - Product Stock Finder

Create a dictionary for product code and stock count. Read a product code and print stock if present; otherwise print "Not Found".

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<string, int> inventory = new Dictionary<string, int>
        {
            { "P101", 25 },
            { "P102", 0 },
            { "P103", 14 }
        };

        string inputCode = Console.ReadLine();
        // TODO: Implement lookup and print result
    }
}

2) Student Marks - Update Existing Key

Store student names and marks. If a student exists, update mark; otherwise add new student.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<string, int> marks = new Dictionary<string, int>
        {
            { "Asha", 78 },
            { "Bala", 82 }
        };

        string student = Console.ReadLine();
        int newMark = int.Parse(Console.ReadLine());
        // TODO: Add or update mark
    }
}

3) Attendance Counter - Frequency Using Dictionary

Given an array of employee IDs, count attendance frequency of each employee.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        int[] employeeIds = { 1001, 1002, 1001, 1003, 1002, 1001 };
        Dictionary<int, int> attendance = new Dictionary<int, int>();
        // TODO: Build frequency map and print
    }
}

4) Login Attempt Tracker - Increment Value

Track failed login attempts per user. Increment attempts whenever a username is received.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        string[] attempts = { "raj", "kavi", "raj", "raj", "kavi" };
        Dictionary<string, int> failedAttempts = new Dictionary<string, int>();
        // TODO: Count attempts and print users with attempts >= 3
    }
}

5) Country Code Resolver - Safe Access

Store country dialing codes and fetch a country code using TryGetValue.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<string, string> dialCodes = new Dictionary<string, string>
        {
            { "India", "+91" },
            { "USA", "+1" },
            { "Japan", "+81" }
        };

        string country = Console.ReadLine();
        // TODO: Use TryGetValue to print code or "Unavailable"
    }
}

6) Course Enrollment - Remove Key

Maintain course name and enrolled count. Remove a cancelled course from dictionary.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<string, int> courses = new Dictionary<string, int>
        {
            { "CSharp", 30 },
            { "SQL", 28 },
            { "Azure", 15 }
        };

        string cancelledCourse = Console.ReadLine();
        // TODO: Remove key if available and print remaining courses
    }
}

7) Price Catalog - Check Key Existence

Given an item name, validate whether it exists in catalog before billing.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<string, decimal> catalog = new Dictionary<string, decimal>
        {
            { "Pen", 12.5m },
            { "Book", 90m },
            { "Bag", 450m }
        };

        string item = Console.ReadLine();
        // TODO: Print item price if exists; else print "Invalid Item"
    }
}

8) City Temperature Board - Iterate Keys and Values

Print each city with temperature and find the hottest city.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<string, int> temperature = new Dictionary<string, int>
        {
            { "Chennai", 38 },
            { "Delhi", 41 },
            { "Bengaluru", 29 }
        };

        // TODO: Iterate and find max temperature city
    }
}

9) Character Counter - String Analytics

Given input string, count occurrences of each character using dictionary.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        string text = Console.ReadLine();
        Dictionary<char, int> charCount = new Dictionary<char, int>();
        // TODO: Build frequency and display sorted output
    }
}

10) Employee Directory - Merge Dictionaries

Merge branch1 and branch2 employee dictionaries. If duplicate key appears, prefer branch2 value.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<int, string> branch1 = new Dictionary<int, string>
        {
            { 101, "Anu" },
            { 102, "Dev" }
        };

        Dictionary<int, string> branch2 = new Dictionary<int, string>
        {
            { 102, "Devika" },
            { 103, "Rahul" }
        };

        // TODO: Merge dictionaries and print final result
    }
}

11) Word Dictionary - Case-Insensitive Keys

Build a dictionary that treats "apple" and "Apple" as same key.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<string, string> meanings = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
        // TODO: Add words and demonstrate case-insensitive retrieval
    }
}

12) Ticket Priority Queue Snapshot - Group Counts

From ticket priorities array (High/Medium/Low), produce a dictionary count per priority.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        string[] priorities = { "High", "Low", "Medium", "High", "High", "Low" };
        Dictionary<string, int> priorityCount = new Dictionary<string, int>();
        // TODO: Count each priority bucket
    }
}

13) Department Budget - Sum of Values

Store budgets for departments and print total budget utilization.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<string, double> budget = new Dictionary<string, double>
        {
            { "IT", 12.5 },
            { "HR", 6.2 },
            { "Finance", 9.1 }
        };

        // TODO: Calculate and print total budget
    }
}

14) Last Seen Activity - DateTime Value Handling

Track last login time for users and print users inactive for more than 30 days.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<string, DateTime> lastLogin = new Dictionary<string, DateTime>
        {
            { "arun", DateTime.Today.AddDays(-10) },
            { "meena", DateTime.Today.AddDays(-45) },
            { "salim", DateTime.Today.AddDays(-60) }
        };

        // TODO: Filter and print inactive users
    }
}

15) API Response Cache - Add If Missing

Use dictionary as cache. Add response only when URL key is not present.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<string, string> cache = new Dictionary<string, string>();
        string url = Console.ReadLine();
        string response = Console.ReadLine();
        // TODO: Cache value only for new URL and print cache size
    }
}

16) Sales By Region - Nested Dictionary Intro

Track region-wise product sales count using nested dictionary.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<string, Dictionary<string, int>> sales = new Dictionary<string, Dictionary<string, int>>();
        // TODO: Add data for region/product and print a summary report
    }
}

17) Duplicate Detector - First Repeated Number

Given integer array, use dictionary to identify first repeating value.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        int[] nums = { 5, 1, 4, 2, 4, 3, 5 };
        Dictionary<int, int> seen = new Dictionary<int, int>();
        // TODO: Print first repeated number
    }
}

18) Transport Route Planner - Invert Dictionary

Convert city-to-route dictionary into route-to-list-of-cities dictionary.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<string, string> cityRoute = new Dictionary<string, string>
        {
            { "Pune", "R1" },
            { "Mumbai", "R2" },
            { "Nashik", "R1" }
        };

        // TODO: Invert and print route-wise cities
    }
}

19) Exam Result Board - Topper Finder

From student marks dictionary, identify topper name(s) with highest mark.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<string, int> scores = new Dictionary<string, int>
        {
            { "Kiran", 92 },
            { "Latha", 96 },
            { "Nitin", 96 },
            { "Pooja", 88 }
        };

        // TODO: Find max score and print all toppers
    }
}

20) Mini Phonebook - CRUD Menu Scenario

Build a menu-driven phonebook using dictionary with Add, Search, Update, Delete operations.

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<string, string> phoneBook = new Dictionary<string, string>();
        bool running = true;

        while (running)
        {
            Console.WriteLine("1.Add 2.Search 3.Update 4.Delete 5.Exit");
            int choice = int.Parse(Console.ReadLine());
            // TODO: Implement menu operations using dictionary
        }
    }
}