Combine two lists in C

In C programming, programmers commonly perform the task of combining two lists for various scenarios like merging datasets or extending arrays dynamically.This is useful when you want to combine information from different sources. In this blog post, you will learn an easy way to combine two lists in C programming. We’ll provide code, explain what it does, and show you the result so you can use this trick in your own programs!

Combine two lists in C- Code

Check out the below code for a better understanding of how to Combine two lists in C.

//Combine two lists in C 
#include <stdio.h>

void combineArrays(int arr1[], int size1, int arr2[], int size2, int result[]) {
    for (int i = 0; i < size1; i++) {
        result[i] = arr1[i];
    for (int i = 0; i < size2; i++) {
        result[size1 + i] = arr2[i];

int main() {
    int arr1[] = {1, 2, 3, 4};
    int arr2[] = {5, 6, 7, 8};
    int size1 = sizeof(arr1) / sizeof(arr1[0]);
    int size2 = sizeof(arr2) / sizeof(arr2[0]);
    int result[size1 + size2];

    combineArrays(arr1, size1, arr2, size2, result);

    printf("Combined array: ");
    for (int i = 0; i < size1 + size2; i++) {
        printf("%d ", result[i]);

    return 0;

Explanation in the code:

The code illustrates how to combine two arrays in C.

The combineArrays function accepts two arrays (arr1 and arr2), their sizes (size1 and size2), and a result array. It first copies elements from arr1 into result, then appends elements from arr2. In the main function, two arrays (arr1 and arr2) are initialized. Their sizes are calculated using sizeof, and the result array is declared to hold the combined elements. The combineArrays function merges arr1 and arr2 into result. Finally, we print the combined array. The for loop iterates over the combined array, outputting each element, resulting in the sequence “1 2 3 4 5 6 7 8”.


Combined array: 1 2 3 4 5 6 7 8 

Possible Errors and Solutions: Combine Two Lists in C

1. Uninitialized Result Array

   Error: Declaring the `result` array without specifying its size.

  Solution: Ensure that you properly size the result array to hold the combined elements from both arrays.

int result[size1 + size2]; // Correctly sized array

2. Incorrect Array Size Calculation

   Error: Using `sizeof` on pointers instead of arrays to calculate sizes.

   Solution: Always use sizeof on the array itself within the scope where you declare it.

  int size1 = sizeof(arr1) / sizeof(arr1[0]); // Correct
    int size2 = sizeof(arr2) / sizeof(arr2[0]); // Correct

3. Array Index Out of Bounds

   Error: Accessing indices outside the bounds of the array due to incorrect loop conditions.

   Solution: Ensure loop conditions accurately reflect the array bounds.

  for (int i = 0; i < size1; i++) {
        result[i] = arr1[i];
    for (int i = 0; i < size2; i++) {
        result[size1 + i] = arr2[i];

4. Incorrect Function Parameters

   Error: Passing incorrect sizes or arrays to the `combineArrays` function.

   Solution: Ensure the function parameters match the expected data types and sizes.

combineArrays(arr1, size1, arr2, size2, result); // Correct parameters

5. Memory Allocation for Dynamic Arrays

   Error: Using dynamic memory allocation without properly allocating and freeing memory.

Solution: Allocate memory for the result array using malloc if its size is not known at compile time, and remember to free the memory afterward.

  int *result = (int *)malloc((size1 + size2) * sizeof(int));
    if (result == NULL) {
        printf("Memory allocation failed");
        return 1; // Exit program if memory allocation fails
    // Use the result array as needed
    free(result); // Free the allocated memory

6. Missing Return Statement in Main

   Error: Forgetting to return an integer value from the `main` function.

   Solution: Always include a return statement to indicate successful completion.

 return 0; // Indicate successful execution

By addressing these common errors and following the solutions, you can ensure your code to combine two lists in C is robust and error-free.

In this blog, we’ve explored the blog ‘Combine two lists in C’, highlighting its educational and practical value. Experiment with this code to enhance your understanding. For more tutorials and courses in Python, C, PHP, HTML, and more, visit Newtum. Engage in programming and enjoy your coding journey. Happy coding!

Combine two lists in C- FAQ

What is the purpose of combining two lists in C?

Combining two lists in C is useful for merging datasets or extending arrays dynamically.

How does the combineArrays function work?

The combineArrays function copies elements from the first array and then appends elements from the second array into the result array.

How do you calculate the size of an array in C?

Use sizeof(arr) / sizeof(arr[0]) to calculate the number of elements in an array.

What should you do if the result array is not properly initialized?

Ensure the result array is correctly sized to hold all elements from both arrays.

How do you handle dynamic memory allocation for combining two lists in C?

Use malloc to allocate memory for the result array and remember to free it afterward.

About The Author

Leave a Reply