Quick Sort

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
void quick(int *, int, int);
int compare = 0, swap = 0;
int main(void) {
  srand((unsigned int) time(NULL));
  printf("Number of trials: ");
  int n;
  scanf("%d", &n);
  int r[n];
  for (int i = 0; i < n; i++) {
    r[i] = rand() % 100;
  }
  for (int i = 0; i < n; i++) printf("%d ", r[i]);
  puts("");
  quick(r, 0, n - 1);
  puts("<クイックソート法>");
  printf("比較回数: %d回\n", compare);
  printf("交換回数: %d回\n", swap);
  for (int i = 0; i < n; i++) printf("%d ", r[i]);
  puts("");
  return 0;
}

void quick(int *a, int left, int right) {
  int i = left;
  int j = right;
  int pivot = a[rand() % (j - i) + i];
  while (1) {
    while (a[i] < pivot) {
      i++;
      compare++;
    }
    while (a[j] > pivot) {
      j--;
      compare++;
    }
    if (i >= j) break;
    int t = a[i];
    a[i] = a[j];
    a[j] = t;
    swap++;
    i++;
    j--;
  }
  if (left < i - 1) quick(a, left, i - 1);
  if (right > j + 1) quick(a, j + 1, right);
}