Implementation of Sorting algotithm in C language

insertion-sort.c

/* compile: gcc -o insertion-sort insertion-sort.c */
#include <stdio.h>

int
main()
{
    int i;
    int A[6] = {5, 2, 4, 6, 1, 3};

    for(i = 1; i < 6; i++) {
        int key, j;

        key = A[i];
        j = i - 1;
        while(j >= 0 && A[j] > key) {
            A[j+1] = A[j];
            j -= 1;
        }
        A[j+1] = key;
    }

    for(i = 0; i < 6; i++)
        printf("%d ", A[i]);
}

merge-sort.c

/* compile: gcc -o merge-sort merge-sort.c */
#include <stdio.h>
#include <limits.h>

void merge(int A[], int p, int q, int r);
void merge_sort(int A[], int p, int r);

int
main()
{
    int i;
    int A[10] = {4, 5, 66, 7, 33, 1, 33, 5, 8, 90};

    merge_sort(A, 0, 10);
    for(i = 0; i < 10; i++)
        printf("%d ", A[i]);
}

void
merge(int A[], int p, int q, int r)
{
    int i, j, k, nl, nr;

    nl = q - p + 1;
    nr = r - q;

    int L[nl+1], R[nr+1];

    for(i = 0; i <= nl; i++)
        L[i] = A[p + i - 1];
    for(j = 0; j <= nr; j++)
        R[j] = A[q + j];

    L[nl + 1] = INT_MAX;
    R[nr + 1] = INT_MAX;

    i = j = 1;
    for(k = p; k <= r; k++) {
        if(L[i] <= R[j]) {
            A[k] = L[i];
            i += 1;
        } else {
            A[k] = R[j];
            j += 1;
        }
    }
}

void
merge_sort(int A[], int p, int r)
{
    int q;

    if(p < r) {
        q = (p+r)/2;
        merge_sort(A, p, q);
        merge_sort(A, q+1, r);
        merge(A, p, q, r);
    }
}

selection-sort.c

/* compile: gcc -o selection-sort selection-sort.c */
#include <stdio.h>

int
main()
{
    int i;
    int A[5] = {30, 3, 40, 100, 5};

    for(i = 0; i < 5; i++) {
        int j, smallest, temp;

        smallest = A[i];
        for(j = i; j < 5; j++) {
            temp = smallest;
            if(A[j] < smallest) {
                smallest = A[j];
                A[j] = temp;
            }
        }

        A[i] = smallest;
    }

    for(i = 0; i < 5; i++)
        printf("%d ", A[i]);

}