The **main difference** between stack and heap is that a **stack is a linear data structure, which organizes data in a sequential manner, while a heap is a nonlinear data structure, which arranges data in a hierarchical manner.**

A data structure is a way of storing and managing data efficiently. Generally, there are two types of data structures as linear and nonlinear data structures. A linear data structure arranges data in a sequential manner. On the other hand, nonlinear data structure organizes data in a hierarchical manner, creating a relationship between data. Thus, overall, the stack is a linear data structure, while the heap is a nonlinear data structure.

### Key Areas Covered

**1. What Stack**

* -Definition, Functionality* **2. What is Heap**

* -Definition, Functionality* **3. Difference Between Stack and Heap**

*-Comparison of key differences*

### Key Terms

*Binary Tree, Linear Data Structure, Heap, Nonlinear Data Structure, Stack *

## What is Stack

Stack is a data structure which is similar to a real-world stack such as a pile of files. The main operations of a stack are pop, push and peep. Pop operation includes inserting an element at the top of the stack whereas push includes removing the topmost element from the stack. Furthermore, the peek operation involves reading the topmost elements without removing it from the stack. However, it is essential to check whether the stack is full or not before inserting elements to the stack. Moreover, the stack is empty if there are no elements in the stack. Importantly, the stack works according to the First In Last Out (FILO) mechanism. In other words, the first inserted element is the last elements to remove from the stack.

Besides all, there are some limitations of stacks. Firstly, the stack memory is limited. Secondly, there is a possibility of stack overflow with the increase in the elements. Finally, it is not possible to access the elements randomly. However, when using small variables etc. the programmer can use a stack as it is faster.

## What is Heap

Heap is a special tree-based data structure. It satisfies two main properties: shape property and heap property. The shape property refers to a heap that is always a complete binary tree in which all levels of the tree are full. The heap property refers to all nodes that are either greater than or equal to or less than or equal to each of its children.

Furthermore, it is possible to categorize a heap based on the values. For example, if the parent nodes are greater than the child nodes, then that is a max heap. On the other hand, if the parent nodes are smaller than their child nodes, it is a min-heap.

The heap sort algorithm allows building a heap data structure from a given array and then arranging the heap in a sorted manner. Further, this algorithm involves two sections: one is creating a heap from an array and removing the largest and smallest element from the heap, and the second is inserting it into the array to create a sorted array.

However, the heap has some drawbacks. Mainly, it takes more time to compute. Also, it takes more time to execute. Finally, the memory management of the heap is more complicated. However, the programmer can consider using heap when it is necessary to allocate a large block of memory.

## Difference Between Stack and Heap

### Definition

A stack is a data structure that serves a collection of elements with two principal operations: push and pop. In contrast, a heap is a balanced binary tree data structure in which the root node is compared with the child nodes to arrange it accordingly.

### Data structure type

Moreover, the stack is a linear data structure, while the heap is a nonlinear (hierarchical) data structure. Thus, this is the main difference between stack and heap.

### Memory allocation

In stack, the memory is allocated in a contiguous block while in a heap, the memory is allocated in random order.

### Flexibility

The size of the stack is fixed whereas it is possible to resize a heap.

### Execution

Furthermore, the stack is faster, whereas heap is slower. Hence, this is another difference between stack and heap.

### Conclusion

In programming, it is good practice to select appropriate data structures to execute the program efficiently. There are various types of data structures, and two of them are stack and heap. The main difference between stack and heap is that a stack is a linear data structure that organizes data in a sequential manner, while heap is a nonlinear data structure that arranges data in a hierarchical manner.

##### References:

1.“What Is Stack Data Structure?” Studytonight, Available here.

2.“Heap Sort Algorithm.” Studytonight, Available here.

##### Image Courtesy:

1.”Simple representation of a stack” By User:Boivie – made in Inkscape, by myself User:Boivie. Based on Image:Stack-sv.png, originally uploaded to the Swedish Wikipedia in 2004 by sv:User:Shrimp (Public Domain) via Commons Wikimedia

2.”Example of a complete binary max heap” By Ermishin – Own work (CC BY-SA 3.0) via Commons Wikimedia

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