C言語でクイックソートの練習

quicksort.c

// -*- mode: c; coding: utf-8 -*-
#include <stdio.h>

void quicksort_internal(int array[], int left, int right, int (*test_func)(int, int)) {
  int pivot;
  int i, j, tmp;
  
  if (left >= right) {
    return;
  }

  i = left;
  j = right;
  pivot = array[i];

  while (1) {
    for (; i < right && test_func(array[i], pivot) > 0; i++);
    for (; j >= left && test_func(array[j], pivot) < 0; j--);

    if (i >= j) {
      break;
    }

    tmp = array[i];
    array[i] = array[j];
    array[j] = tmp;
    i++;
    j--;
  }

  quicksort_internal(array, left, i - 1, test_func);
  quicksort_internal(array, j + 1, right, test_func);
}

void quicksort(int array[], int size, int (*test_func)(int, int)) {
  quicksort_internal(array, 0, size - 1, test_func);
}

int asc(int a, int b) {
  return (a == b) ? 0 : (a < b) ? 1 : -1;
}

int desc(int a, int b) {
  return (a == b) ? 0 : (a > b) ? 1 : -1;
}

int main(int argc, char *argv[]) {
  int a[] = { 3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9, 7, 9 };
  int i;
  int size = sizeof(a) / sizeof(a[0]);

  puts("Array:");
  for (i = 0; i < size; i++) {
    printf("%d ", a[i]);
  }
  puts("");

  puts("Asc:");
  quicksort(a, size, asc);
  for (i = 0; i < size; i++) {
    printf("%d ", a[i]);
  }
  puts("");

  puts("Desc:");
  quicksort(a, size, desc);
  for (i = 0; i < size; i++) {
    printf("%d ", a[i]);
  }
  puts("");

  return 0;
}