Why Hash Map Exists and What Problem It Solves in DSA C - See It Work

Why Hash Map Exists and What Problem It Solves

📖 Scenario: Imagine you have a big box of keys and you want to find the right key quickly to open a door. Searching one by one takes too long. A hash map is like a magic box that helps you find the right key fast.

🎯 Goal: You will create a simple program that stores and finds phone numbers by names using a hash map concept. This will show why hash maps exist and how they solve the problem of slow searching.

📋 What You'll Learn

Create an array of strings called names with these exact entries: "Alice", "Bob", "Charlie"

Create an array of integers called phone_numbers with these exact entries: 12345, 67890, 54321

Create an integer variable called size and set it to 3

Write a function called find_phone_number that takes char* name, char* names[], int phone_numbers[], and int size and returns the phone number for the given name or -1 if not found

Use a for loop with variable i to search through names inside find_phone_number

Print the phone number for "Bob" using find_phone_number

💡 Why This Matters

🌍 Real World

Hash maps help apps like phonebooks, contact lists, and databases find information fast without checking every item.

💼 Career

Understanding hash maps is key for software developers to write efficient code for searching and storing data.

1

Create the Data Setup

Create an array of strings called names with these exact entries: "Alice", "Bob", "Charlie". Also create an array of integers called phone_numbers with these exact entries: 12345, 67890, 54321.

DSA C

# Create arrays names and phone_numbers with given values
# Your code here

Hint

Use arrays to store the names and phone numbers exactly as shown.

2

Add Size Variable

Create an integer variable called size and set it to 3 to represent the number of entries.

DSA C

#include 

char* names[] = {"Alice", "Bob", "Charlie"};
int phone_numbers[] = {12345, 67890, 54321};

// Create size variable
# Your code here

Hint

Use an integer variable named size and assign it the value 3.

3

Write the Search Function

Write a function called find_phone_number that takes char* name, char* names[], int phone_numbers[], and int size. Use a for loop with variable i to search through names. If name matches names[i], return phone_numbers[i]. If not found, return -1.

DSA C

#include 
#include 

char* names[] = {"Alice", "Bob", "Charlie"};
int phone_numbers[] = {12345, 67890, 54321};

int size = 3;

// Write find_phone_number function
# Your code here

Hint

Use strcmp to compare strings inside the loop.

4

Print the Phone Number for Bob

Use printf to print the phone number for "Bob" by calling find_phone_number("Bob", names, phone_numbers, size).

DSA C

#include 
#include 

char* names[] = {"Alice", "Bob", "Charlie"};
int phone_numbers[] = {12345, 67890, 54321};

int size = 3;

int find_phone_number(char* name, char* names[], int phone_numbers[], int size) {
    for (int i = 0; i < size; i++) {
        if (strcmp(name, names[i]) == 0) {
            return phone_numbers[i];
        }
    }
    return -1;
}

int main() {
    // Print phone number for Bob
# Your code here
    return 0;
}

Hint

Use printf("%d\n", ...) to print the phone number.