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

// from Van Wyk, chapter 10, page 233++
typedef struct heapslot heapslot;
struct heapslot {
  int key;
  int value;
} ;

#define MAXHEAP 4

heapslot * heap;
int heapnum;
int maxheap;

bool empty(){
  return heapnum == 0;
}

void demand(int cond, char * msg) {
  if (! cond) {
    fprintf(stderr, msg);
    exit(1);
  }
  return;
}


void printHeap(){
  printf("HEAP: ");
  for(int i = 1; i <= heapnum; i++){
    printf("[%d: %d/%d] ", i, heap[i].key, heap[i].value);
  }
  printf("\n");
}

int findmin(){
  demand( !empty(), "findmin not allowed on empty heap\n");
  return heap[1].value;
}

void initheap(){
  heapnum = 0;
  maxheap = MAXHEAP;
  heap = malloc(maxheap * sizeof(heap));
  heap[0].key = INT_MIN;
}

void swap(heapslot *s1, heapslot *s2){
  heapslot temp;
  printf("SWAP: %d <=> %d\n", s1->key, s2->key);
  temp = *s1;
  *s1 = *s2;
  *s2 = temp;
}

void insert(int key, int value){
  int cur, parent;
  printf("INSERT: %d, %d ", key, value);

  //demand(heapnum < maxheap, "heap overflow\n");
  while(heapnum  >= maxheap) {
    maxheap *= 2;
    printf("\nExpanding heap size to %d\n", maxheap);
    heap = realloc(heap, sizeof(*heap) * maxheap);
    demand(heap != 0, "malloc fail in insert\n");
  }


  cur = ++heapnum;
  heap[cur].key = key;
  heap[cur].value = value;
  parent = cur/2;
  while (heap[parent].key > heap[cur].key) {
    printf("\n--");
    printHeap();
    demand(parent > 0, "inserted item rising past root\n");
    swap(&heap[parent], &heap[cur]);
    cur = parent;
    parent = cur/2;
  }
  printHeap();
}

void deletemin(){
  int cur, child;
  printf("DELETEMIN: ");
  demand(! empty(), "deletemin not allowed on empty heap\n");
  heap[1] = heap[heapnum--];
  cur = 1;
  child = 2;
  while (child <= heapnum) {
    printf("\n--");
    printHeap();
    if (child < heapnum &&
	heap[child+1].key < heap[child].key)
      child++;
    if (heap[cur].key > heap[child].key) {
      demand(child <= heapnum, "falling past leaves\n");
      swap(&heap[cur], &heap[child]);
      cur = child;
      child = 2*cur;
    } else
      break;
  }
  printHeap();
}



int main(int argc, char ** argv){

  initheap();

  //printHeap();

  if (argc > 1) {
    for (int i=1; i < argc; i++) {
      int val = atoi(argv[i]);
      if (val > 0) {
	insert(val, val*val);
      } else {
	deletemin();
      }
    }
    exit(1);
  } else {
    fprintf(stderr, "Usage: heap [numbers]+\n");
    exit(1);
  }
}