BUPT-homework/semester3/pset3/7-1-Binary-Heap.c

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

typedef struct heap {
  int *arr;
  int capacity;
  int size;
} heap;

heap *newHeap(int size) {
  heap *new = malloc(sizeof(heap));

  new->arr = malloc(sizeof(int) * size);

  new->size = 0;
  new->capacity = size;

  return new;
}

void swap(int *l, int *r) {
  int tmp = *r;
  *r = *l;
  *l = tmp;
}

int max(int l, int r) { return (l > r) ? l : r; }

int parent(int i) { return (i - 1) / 2; }

int left(int i) { return i * 2 + 1; }

int right(int i) { return i * 2 + 2; }

void insert(heap *h, int val) {
  int i = h->size++;

  h->arr[i] = val;

  while (i != 0 && h->arr[i] < h->arr[parent(i)]) {
    swap(&h->arr[i], &h->arr[parent(i)]);
    i = parent(i);
  }
}

void heapify(heap *h, int i) {
  int smallest = i;
  int l = left(i);
  int r = right(i);

  // comparing size is important!
  if (l < h->size && h->arr[smallest] > h->arr[l]) {
    smallest = l;
  }
  if (r < h->size && h->arr[smallest] > h->arr[r]) {
    smallest = r;
  }

  if (smallest != i) {
    swap(&h->arr[smallest], &h->arr[i]);
    heapify(h, smallest);
  }
}

void buildHeap(heap *h) {
  int start = h->size / 2 - 1;

  while (start >= 0) {
    heapify(h, start--);
  }
}

void print(int *array, int size) {
  for (int i = 0; i < size - 1; i++) {
    printf("%d,", array[i]);
  }
  printf("%d\n", array[size - 1]);
}

int main(void) {
  int size;
  scanf("%d", &size);

  int tmp;
  heap *h1 = newHeap(size);
  heap *h2 = newHeap(size);
  // make sure this one.
  h2->size = size;

  for (int i = 0; i < size; i++) {
    scanf("%d,", &tmp);
    h2->arr[i] = tmp;
    insert(h1, tmp);
  }

  buildHeap(h2);
  print(h1->arr, size);
  print(h2->arr, size);

  return 0;
}