Merge Two Arrays in C

To merge two arrays in C, we create a new array with a size equal to the sum of both arrays and copy elements from both arrays into it. We use loops to iterate through the source arrays and store elements sequentially in the merged array.

Examples of Merging Two Arrays

1. Merging Two Arrays into a Third Array Using a for Loop

In this example, we declare two integer arrays and merge them into a third array using a for loop.

main.c

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#include <stdio.h>

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

    // Copy elements of arr1 into merged
    for (int i = 0; i < size1; i++) {
        merged[i] = arr1[i];
    }

    // Copy elements of arr2 into merged
    for (int i = 0; i < size2; i++) {
        merged[size1 + i] = arr2[i];
    }

    // Print merged array
    printf("Merged Array: ");
    for (int i = 0; i < size1 + size2; i++) {
        printf("%d ", merged[i]);
    }

    return 0;
}

Explanation:

  1. We declare two integer arrays, arr1 and arr2, and determine their sizes using sizeof().
  2. A third array, merged, is created with a size equal to the sum of size1 and size2.
  3. We use a for loop to copy all elements from arr1 into merged.
  4. Another for loop copies elements from arr2 into the next available positions of merged.
  5. Finally, a loop iterates through merged to print all elements in sequence.

Output:

Merged Array: 1 2 3 4 5 6

2. Merging Two Arrays Using a Function

In this example, we define a function to merge two arrays, making our program more reusable and structured.

main.c

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#include <stdio.h>

void mergeArrays(int arr1[], int size1, int arr2[], int size2, int merged[]) {
    for (int i = 0; i < size1; i++) {
        merged[i] = arr1[i];
    }
    for (int i = 0; i < size2; i++) {
        merged[size1 + i] = arr2[i];
    }
}

int main() {
    int arr1[] = {10, 20, 30};
    int arr2[] = {40, 50, 60};
    int size1 = sizeof(arr1) / sizeof(arr1[0]);
    int size2 = sizeof(arr2) / sizeof(arr2[0]);
    int merged[size1 + size2];

    // Call function to merge arrays
    mergeArrays(arr1, size1, arr2, size2, merged);

    // Print merged array
    printf("Merged Array: ");
    for (int i = 0; i < size1 + size2; i++) {
        printf("%d ", merged[i]);
    }

    return 0;
}

Explanation:

  1. We define a function mergeArrays() that takes two arrays, their sizes, and an output array as arguments.
  2. Inside the function, two for loops copy elements from arr1 and arr2 into merged.
  3. In main(), we declare two integer arrays and determine their sizes.
  4. We call mergeArrays() to merge the two arrays into merged.
  5. A loop iterates through merged to print the merged elements.

Output:

Merged Array: 10 20 30 40 50 60

Conclusion

In this tutorial, we explored how to merge two arrays in C with different approaches:

  1. Using a for Loop: A simple approach to copy elements sequentially.
  2. Using a Function: A structured and reusable way to merge arrays.