QuickSort with Lomuto partition

quicksort.c

#include <stdio.h>

/**
 * [ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15]
 * [ 8, 29, 60,  6,  4, 93, 85,  5, 26, 29,  2, 69, 83, 72, 43, 50]
 * Pivot 50 (a[r])
 * I 0
 * Leftwall 0
 *
 * Step 1)
 * [ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15]
 * [ 8, 29, 60,  6,  4, 93, 85,  5, 26, 29,  2, 69, 83, 72, 43, 50]
 * I 0
 * Leftwall 1
 *
 * Step 2)
 * [ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15]
 * [ 8, 29, 60,  6,  4, 93, 85,  5, 26, 29,  2, 69, 83, 72, 43, 50]
 * I 1
 * Leftwall 2
 *
 * Step 3)
 * [ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15]
 * [ 8, 29,  6, 60,  4, 93, 85,  5, 26, 29,  2, 69, 83, 72, 43, 50]
 * I 3
 * Leftwall 3
 *
 * Step 4)
 * [ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15]
 * [ 8, 29,  6,  4, 60, 93, 85,  5, 26, 29,  2, 69, 83, 72, 43, 50]
 * I 4
 * Leftwall 4
 *
 * Step 5)
 * [ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15]
 * [ 8, 29,  6,  4,  5, 93, 85, 60, 26, 29,  2, 69, 83, 72, 43, 50]
 * I 7
 * Leftwall 5
 *
 * Step 6)
 * [ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15]
 * [ 8, 29,  6,  4,  5, 26, 85, 60, 93, 29,  2, 69, 83, 72, 43, 50]
 * I 8
 * Leftwall 6
 *
 * Step 7)
 * [ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15]
 * [ 8, 29,  6,  4,  5, 26, 29, 60, 93, 85,  2, 69, 83, 72, 43, 50]
 * I 9
 * Leftwall 7
 *
 * Step 8)
 * [ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15]
 * [ 8, 29,  6,  4,  5, 26, 29,  2, 93, 85, 60, 69, 83, 72, 43, 50]
 * I 10
 * Leftwall 8
 *
 * Step 9)
 * [ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15]
 * [ 8, 29,  6,  4,  5, 26, 29,  2, 43, 85, 60, 69, 83, 72, 93, 50]
 * I 14
 * Leftwall 9
 *
 * Step Finale)
 *
 *                                   leftwall                    r
 *                                       |                       |
 *                                       |                       |
 *                                       v                       v
 * [ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15]
 * [ 8, 29,  6,  4,  5, 26, 29,  2, 43, 85, 60, 69, 83, 72, 93, 50]
 *
 * Scambio pivot con leftwall
 * [ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15]
 * [ 8, 29,  6,  4,  5, 26, 29,  2, 43, 50, 60, 69, 83, 72, 93, 85]
 *
 * Array sinistro: (tutti minori di 50)
 *
 *   l                         leftwall - 1
 *   |                               |
 *   |                               |
 *   v                               v
 * [ 8, 29,  6,  4,  5, 26, 29,  2, 43]
 *
 *
 * Array destro: (tutti maggiori di 50)
 *
 * leftwall + 1            r
 *     |                   |
 *     |                   |
 *     v                   v
 *   [60, 69, 83, 72, 93, 85]
 *
 * Valore di ritorno (pivot):
 *
 * leftwall
 *     |
 *     |
 *     v
 *   [50]
 */
int partition(int *A, int l, int r) {
    int pivot = A[r];
    int leftWall = l;

    int tmp;
    for (int i = l; i < r; ++i) {
        if (A[i] <= pivot) {
            if (i != leftWall) {
                tmp = A[i];
                A[i] = A[leftWall];
                A[leftWall] = tmp;
            }

            ++leftWall;
        }
    }

    if (r != leftWall) {
        tmp = A[r];
        A[r] = A[leftWall];
        A[leftWall] = tmp;
    }

    return leftWall;
}

void quickSort(int *A, int l, int r) {
    if (l >= r) {
        return;
    }

    int q = partition(A, l, r);
    quickSort(A, l, q - 1);
    quickSort(A, q + 1, r);
}

int main() {
    int A[] = {
            8, 29, 60, 6, 4, 93, 85, 5, 26, 29, 2, 69, 83, 72, 43, 50
    };

    int length = sizeof(A) / sizeof(A[0]);
    quickSort(A, 0, length - 1);

    printf("A[%d] = {\n\t", length);
    for (int i = 0; i < length; ++i) {
        if (i != 0) {
            printf(", ");
        }

        printf("%2d", A[i]);
    }
    printf("\n}\n");

    return 0;
}