heap_binary_min.c

/************************************************************
Name:           Dhruba Saha
Roll No:        B.Sc(Sem-IV)-04
Program No:     22B
Program Name:   Write a C program to create a binary minheap.
Date:           11/06/2022
*************************************************************/

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

void inputArr(int *arr, int n);
void minHeapify(int *arr, int n, int i);
void buildMinHeap(int *arr, int n);
void printArr(int *arr, int n);

void main() {
  int n, *arr;

  printf("Enter the number of elements: ");
  scanf("%d", &n);

  arr = (int *)malloc(n * sizeof(int));

  inputArr(arr, n);

  printf("Before min heapify:\n");
  printArr(arr, n);

  buildMinHeap(arr, n);

  printf("After min heapify:\n");
  printArr(arr, n);

  free(arr);
}

void inputArr(int *arr, int n) {
  int i;

  for (i = 0; i < n; i++) {
    printf("Enter the element %d:\n", i + 1);
    scanf("%d", &arr[i]);
  }
}

void minHeapify(int *arr, int n, int i) {
  int l, r, smallest, temp;

  l = 2 * i + 1;
  r = 2 * i + 2;
  smallest = i;

  if (l < n && arr[l] < arr[smallest])
    smallest = l;
  if (r < n && arr[r] < arr[smallest])
    smallest = r;

  if (smallest != i) {
    temp = arr[i];
    arr[i] = arr[smallest];
    arr[smallest] = temp;

    minHeapify(arr, n, smallest);
  }
}

void buildMinHeap(int *arr, int n) {
  int i;

  for (i = n / 2 - 1; i >= 0; i--)
    minHeapify(arr, n, i);
}

void printArr(int *arr, int n) {
  int i;

  for (i = 0; i < n; i++)
    printf("%d ", arr[i]);
  printf("\n");
}

/*
Enter the number of elements: 5
Enter the element 1:
21
Enter the element 2:
23
Enter the element 3:
56
Enter the element 4:
71
Enter the element 5:
2
Before min heapify:
21 23 56 71 2
After min heapify:
2 21 56 71 23
*/