Data Structures

This category contains all the posts related to data structures. For e.g.: Hash Tables, Linked Lists, Trees, Graphs, Heaps, Tries etc..

Understanding Heap Sort

Heap Sort is one of the efficient sorting algorithms with a guaranteed worst case running time of O(NlogN). This is an in place sorting algorithm but it does not offer stable sorting. In place Sorting: A sorting algorithm which sorts the input using very small or no extra space. It means that the input data is overwritten by the resulting output data. Stable Sorting: A stable sorting algorithm is one, in which the relative order of equal keys is preserved. It means if there are non unique keys in the input data, then their relative order of occurrence in the input as well as output rem...
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Operations on a Heap

Introduction In this post, we will try to put together all the leanings from the previous posts and define the basic operations on a heap. Also, we will try and derive the running time of each such operation and write code for the same. Also, we will discuss an interesting problem statement which can be easily solved using the heap property. Basic Operations on Heap The heap can support the following basic operations as any other data structure IncreaseKey - Changes the key value of a given node to a new value. It is assumed that the new value is at least as big as the current value....
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Building Heaps from an array of keys

[nextpage title="Introduction"] In the last post we learnt the basics of the heap data structure, its array and tree representations. We also learnt about the heap property and its significance. In the process of learning we understood that a given node can be disturbed and the heap property needs to be restored using the Heapify operation. Here in this post, we will try building heaps from an array of keys. Building Heaps Let us think about the easiest way to build a heap. Assume we are given the below array A: This clearly is not satisfying the max heap property because the root ...
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Understanding the Heap Datastructure

Introduction Heap(specifically binary heap) is a special data structure which can be viewed as a nearly complete binary tree. This post is mostly focused on understanding the heap datastructure The first few impressions about heap after reading the above line: The height of the binary tree would be minimum. For e.g.: if the tree has N nodes, the height would be logN. The tree can also be stored in an array, in fact it would be easier to store this tree in an array (because it is complete). This makes it an awesome data structure because the minimum height guarantees logN running ti...
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Single Source Shortest Path – Directed Acyclic Graph

[nextpage title="Introduction"] Directed Acyclic Graph is a very special graph and has the following properties: The edges of this graph are directed, it means all the edges have a designated direction. There is no cycle in the graph, which means that a path will never contain one vertex more than once. We referred to these kind of graphs in the topological ordering post. Here we discuss the algorithm to find single source shortest path in such graphs. The good part is that unlike Dijkstra and Bellman Ford this can be solved in linear time O(E+V). This algorithm for finding sho...
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