Simple implementation of quick sort

quicksort.c

void quicksort(int* a, int n){
    int i, last;
    if(n <= 1) return;
    swap(a, 0, rand()%n);
    last = 0;
    for(i=1;i<n;i++) if(a[i] < a[0]) swap(a, ++last, i);
    swap(a, 0, last);
    quicksort(a, last);
    quicksort(a+last+1, n-last-1);
}