heapsort

#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#include <iso646.h>
#include <stdlib.h>
#include <time.h>

void swap(int *x, int *y) {
    int tmp = x;
    *x = *y;
    *y = tmp;
}

void heapify(int *arr, int size, size_t i) {
    size_t max;
    while (2 * i + 1 < size) {
        max = arr[i] > arr[i * 2 + 1] ? i : i * 2 + 1;

        if (2 * i + 2 < size)
            max = arr[max] > arr[i * 2 + 2] ?
                    max : i * 2 + 2;

        swap(arr + i, arr + max);
        if (i == max)
            break;
        i = max;
    }
}

void make_heap(int *arr, size_t size) {
    for (size_t i = size / 2; i > 0; --i)
        heapify(arr, size, i);
    heapify(arr, size, 0);
}

void heapsort(int *arr, size_t length) {
    make_heap(arr, length);
    while (length > 0) {
        swap(arr, arr + (--length));
        heapify(arr, length, 0);
    }
}

const char IN_FILE[] = "heapsort.in";
const char OUT_FILE[] = "heapsort.out";

int main() {
    FILE *in = fopen(IN_FILE, "r"),
         *out = fopen(OUT_FILE, "w");
    int n, *arr;
    fscanf(in, "%d", &n);
    arr = malloc(n * sizeof(int));
    for (int i = 0; i < n; ++i)
        fscanf(in, "%d", arr + i);
    heapsort(arr, n);
    for (int i = 0; i < n; ++i)
        fprintf(out, "%d ", arr[i]);
    fprintf(out, "\n");
    return 0;
}