realloc function - Mini Project: Build & Apply

Using the realloc Function in C

📖 Scenario: You are managing a list of daily temperatures stored in a dynamic array in C. Sometimes, you need to add more days to the list, so you must resize the array safely.

🎯 Goal: Learn how to use the realloc function to resize a dynamic array in C while preserving existing data.

📋 What You'll Learn

Create a dynamic array of integers with initial size 3

Create a variable new_size to hold the new size of the array

Use realloc to resize the array to new_size

Print all elements of the resized array

💡 Why This Matters

🌍 Real World

Dynamic arrays are useful when you don't know the exact amount of data in advance, like reading sensor data or user input.

💼 Career

Understanding memory management and resizing arrays is important for systems programming, embedded development, and performance-critical applications.

1

Create the initial dynamic array

Write code to create a dynamic array called temps of integers with initial size 3 using malloc. Initialize the array with values 20, 22, and 19.

C

#include 
#include 

int main() {
    // Create dynamic array temps with size 3 and initialize values
    // Your code here

Need a hint?

Use malloc to allocate memory for 3 integers and assign it to temps. Then assign values to each index.

2

Create a new size variable

Add a variable called new_size and set it to 5 to represent the new size of the array.

C

#include 
#include 

int main() {
    int *temps = malloc(3 * sizeof(int));
    temps[0] = 20;
    temps[1] = 22;
    temps[2] = 19;
    // Create new_size variable and set to 5
    // Your code here

Need a hint?

Declare an integer variable new_size and assign it the value 5.

3

Resize the array using realloc

Use realloc to resize the temps array to new_size. Assign the result back to temps. Then initialize the new elements temps[3] and temps[4] with values 21 and 23.

C

#include 
#include 

int main() {
    int *temps = malloc(3 * sizeof(int));
    temps[0] = 20;
    temps[1] = 22;
    temps[2] = 19;
    int new_size = 5;
    // Resize temps using realloc to new_size
    // Initialize temps[3] = 21 and temps[4] = 23
    // Your code here

Need a hint?

Use temps = realloc(temps, new_size * sizeof(int)) to resize. Then assign values to the new indexes.

4

Print all elements of the resized array

Use a for loop with variable i from 0 to new_size - 1 to print each element of temps on its own line. Then free the allocated memory.

C

#include 
#include 

int main() {
    int *temps = malloc(3 * sizeof(int));
    temps[0] = 20;
    temps[1] = 22;
    temps[2] = 19;
    int new_size = 5;
    temps = realloc(temps, new_size * sizeof(int));
    temps[3] = 21;
    temps[4] = 23;
    // Print all elements of temps using a for loop
    // Free the allocated memory
    // Your code here

Need a hint?

Use a for loop to print each element with printf. Don't forget to call free(temps) at the end.