What Is a Heap Data Structure in C?


Larry Thompson

A heap is a data structure that stores a collection of elements. It is commonly used in computer science to efficiently manage memory allocation. In C, a heap is implemented as a dynamically allocated array, where each element represents a block of memory.

How Does a Heap Work?

A heap works by maintaining a complete binary tree structure. This means that each level of the tree, except possibly the last one, is fully filled, and all nodes are left-aligned. The tree can be represented using an array, where the index of each element corresponds to its position in the tree.

There are two types of heaps: max heaps and min heaps. In a max heap, the value of each node is greater than or equal to the values of its children. Conversely, in a min heap, the value of each node is less than or equal to the values of its children.

Heap Operations

A heap supports several important operations:

  • Insertion: Adding an element to the heap while maintaining the heap property.
  • Deletion: Removing an element from the heap while maintaining the heap property.
  • Peek: Retrieving the value of the root (topmost) element without modifying the heap.

The insertion and deletion operations are crucial for managing dynamic memory allocation efficiently. When allocating memory dynamically in C, we can use functions like `malloc` or `calloc` to request memory from the operating system. However, freeing this memory when it is no longer needed is equally important to prevent memory leaks.

The malloc and free Functions

In C, we use the `malloc` function to dynamically allocate memory on the heap. This function takes the number of bytes to allocate as an argument and returns a pointer to the allocated memory block.

Here is an example:


int main() {
    int* ptr = (int*)malloc(sizeof(int));
    if (ptr == NULL) {
        printf("Memory allocation failed\n");
        return 1;
    *ptr = 42;
    printf("Value: %d\n", *ptr);
    return 0;

The `free` function is used to deallocate memory that was previously allocated using `malloc`. It takes a pointer to the memory block as an argument and releases it back to the operating system.


Heaps are an essential data structure in C for managing dynamic memory allocation. Understanding how heaps work and how to perform basic operations on them is crucial for writing efficient and reliable C programs.

In this article, we covered the basics of heaps, including their structure, types, and operations. We also touched upon the importance of functions like `malloc` and `free` for managing memory on the heap.

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