merge_sort.c

#include <stdlib.h>
#include <stdio.h>
#include <time.h>

#define N 10

int sort[N];
int buffer[N];

void mergeSort(int n, int x[]){
    int i, j, k, m;
    if ( n <= 1 ) {
        return;
    }

    m = n / 2;
    mergeSort(m, x);
    mergeSort(n - m, x + m);

    for ( i = 0; i < m ; i++ ) {
        buffer[i] = x[i];
    }

    i = k = 0;
    j = m;

    while ( i < m && j < n ) {
        if ( buffer[i] <= x[j] )
            x[k++] = buffer[i++];
        else 
            x[k++] = x[j++];
    }

    while ( i < m ) {
        x[k++] = buffer[i++];
    }
}

int main(void)
{
    int i;
    
    srand((unsigned int) time(NULL));

    for ( i = 0; i < N; i++ ) {
        sort[i] = rand();
        printf("%010d ", sort[i]);
    }

    printf("\n\nstart..\n\n");
    mergeSort(N, sort);
    
    for ( i = 0; i < N; i++ ) {
        printf("%010d ", sort[i]);
    }

    return EXIT_SUCCESS;
}