Implementation of the merge sort algorithm in C

main.c

#include <stdio.h>

void merge(int* input, int left, int middle, int right) {
    // variables for indices in loops
    // z is used to keep the input index
    int i, j, z = left;

    // calculating the lenght of the copy array
    int lenght = right - left + 1;
    // creating the copy array
    int copy[lenght];

    // copying the input array to the copy array
    for (i = 0; i < lenght; i++) {
        // considering the left index to copy the array
        copy[i] = input[left + i];
    }

    // calculating the copy left index
    int copyLeft = middle - left + 1;
    // calculating the copy right index
    int copyRight = right - middle;

    // comparing the elements of the copy array and sorting them
    for (i = 0, j = 0; i < copyLeft && j < copyRight; z++) {
        // comparing left and right of the copy
        if (copy[i] <= copy[copyLeft + j]) {
            // adding left element to input
            input[z] = copy[i++];
            continue;
        }

        // adding right element to input
        input[z] = copy[copyLeft + j++];
    }

    // adding the remaining elements to the input array
    while (i < copyLeft) input[z++] = copy[i++];
    while (j < copyRight) input[z++] = copy[copyLeft + j++];
}

void sort(int* input, int left, int right) {
    // If the left index is greater than or equal to the right index, the sort is complete
    if (left >= right) return;

    // Calculating the middle index
    int middle = (left + right) / 2;

    // recusirve merge function to sort of the left at the middle of the array
    sort(input, left, middle);
    // recusirve merge function to sort of the middle at the right of the array
    sort(input, middle + 1, right);

    // Check if the array is already sorted
    if (input[middle] <= input[middle + 1]) return;

    // merge the array
    merge(input, left, middle, right);
}

void mergeSort(int* input, int lenght) {
    // calling the sort function
    sort(input,0, lenght - 1);
}

int main() {
    int array[] = {38, 27, 43, 3, 9, 82, 10, 20, 100, 1, 2, 4, 3, 5, 77};
    int lenght = sizeof(array) / sizeof(array[0]);

    mergeSort(array, lenght);

    for (int i = 0; i < lenght; i++) {
        printf("%d ", array[i]);
    }

    return 0;
}