Book Image

PHP 7 Data Structures and Algorithms

By : Mizanur Rahman
5 (1)
Book Image

PHP 7 Data Structures and Algorithms

5 (1)
By: Mizanur Rahman

Overview of this book

PHP has always been the the go-to language for web based application development, but there are materials and resources you can refer to to see how it works. Data structures and algorithms help you to code and execute them effectively, cutting down on processing time significantly. If you want to explore data structures and algorithms in a practical way with real-life projects, then this book is for you. The book begins by introducing you to data structures and algorithms and how to solve a problem from beginning to end using them. Once you are well aware of the basics, it covers the core aspects like arrays, listed lists, stacks and queues. It will take you through several methods of finding efficient algorithms and show you which ones you should implement in each scenario. In addition to this, you will explore the possibilities of functional data structures using PHP and go through advanced algorithms and graphs as well as dynamic programming. By the end, you will be confident enough to tackle both basic and advanced data structures, understand how they work, and know when to use them in your day-to-day work

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Table of Contents (14 chapters)
Preface
Preface
What this book covers
What you need for this book
Who this book is for
Conventions
Reader feedback
Customer support
Free Chapter
1
Introduction to Data Structures and Algorithms
Introduction to Data Structures and Algorithms
Importance of data structures and algorithms
Understanding Abstract Data Type (ADT)
Different data structures
Solving a problem - algorithmic approach
Writing pseudocode
Algorithm analysis
Understanding the big O (big oh) notation
Standard PHP Library (SPL) and data structures
Summary
2
Understanding PHP Arrays
Understanding PHP Arrays
Understanding PHP arrays in a better way
Using an array as flexible storage
Use of multi-dimensional arrays to represent data structures
Performance comparison between a regular PHP array and SplFixedArray
Understanding hash tables
Implementing struct using a PHP array
Implementing sets using a PHP array
Best usage of a PHP array
PHP array, is it a performance killer?
Summary
3
Using Linked Lists
Using Linked Lists
What is a linked list?
Different types of linked list
Inserting, deleting, and searching for an item
Understanding complexity for linked lists
Making the linked list iterable
Building circular linked list
Implementing a doubly linked list in PHP
Doubly linked list operations
Complexity for doubly linked lists
Using PHP SplDoublyLinkedList
Summary
4
Constructing Stacks and Queues
Constructing Stacks and Queues
Understanding stack
Implementing a stack using PHP array
Understanding complexity of stack operations
Implementing stack using linked list
Using SplStack class from SPL
Real life usage of stack
Understanding queue
Using SplQueue class from SPL
Understanding priority queue
Implementing priority queue using linked list
Implement a priority queue using SplPriorityQueue
Implementing a circular queue
Creating a double - ended queue (deque)
Summary
5
Applying Recursive Algorithms - Recursion
Applying Recursive Algorithms - Recursion
Understanding recursion
Different types of recursions
Building an N-level category tree using recursion
Finding files and directories using recursion
Analyzing recursive algorithms
Maximum recursion depth in PHP
Using SPL recursive iterators
Using the PHP built-in function array_walk_recursive
Summary
6
Understanding and Implementing Trees
Understanding and Implementing Trees
Tree definition and properties
Implementing a tree using PHP
Different types of tree structures
Understanding a binary tree
Implementing a binary tree
Creating a binary tree using a PHP array
Understanding the binary search tree
Constructing a binary search tree
Tree traversal
Complexity of different tree data structures
Summary
7
Using Sorting Algorithms
Using Sorting Algorithms
Understanding sorting and their types
Understanding bubble sort
Understanding selection sort
Understanding insertion Sort
Understanding divide-and-conquer technique for sorting
Understanding merge sort
Understanding quick sort
Understanding bucket sort
Using PHP's built-in sorting function
Summary
8
Exploring Search Options
Exploring Search Options
Linear searching
Binary search
Interpolation search
Exponential search
Search using hash table
Tree searching
Summary
9
Putting Graphs into Action
Putting Graphs into Action
Understanding graph properties
Types of graphs
Revisiting BFS and DFS for graphs
Topological sorting using Kahn's algorithm
Shortest path using the Floyd-Warshall algorithm
Single source shortest path using Dijkstra's algorithm
Finding the shortest path using the Bellman-Ford algorithm
Understanding the minimum spanning tree (MST)
Implementing Prim's spanning tree algorithm
Kruskal's algorithm for spanning tree
Summary
10
Understanding and Using Heaps
Understanding and Using Heaps
What is a heap?
Heap operations
Implementing a binary heap in PHP
Analyzing the complexity of heap operations
Using heaps as a priority queue
Using heap sort
Using SplHeap, SplMaxHeap, and SplMinHeap
Summary
11
Solving Problems with Advanced Techniques
Solving Problems with Advanced Techniques
Memoization
Pattern matching algorithms
Implementing Knuth-Morris-Pratt algorithm
Greedy algorithms
Implementing Huffman coding algorithm
Understanding dynamic programming
0 - 1 knapsack
Finding the longest common subsequence-LCS
DNA sequencing using dynamic programming
Backtracking to solve puzzle problem
Collaborative filtering recommendation system
Using bloom filters and sparse matrix
Summary
12
PHP Built-In Support for Data Structures and Algorithms
PHP Built-In Support for Data Structures and Algorithms
Built-in PHP features for data structure
SPL classes
Built-in PHP algorithms
Hashing
Built-in support through PECL
Vector
Summary
13
Functional Data Structures with PHP
Functional Data Structures with PHP
Understanding functional programming with PHP
Getting started with Tarsana
Implementing stack
Implementing a queue
Implementing a tree
Summary

Solving a problem - algorithmic approach

So far we have discussed different types of data structures and their usage. But, one thing we have to remember is that just putting data in a proper structure might not solve our problems. We need to find solutions to our problems using the help of data structures or, in other words, we are going to solve problems using data structures. We need algorithms to solve our problem.

An algorithm is a step by step process which defines the set of instructions to be executed in a certain order to get a desired output. In general, algorithms are not limited to any programming language or platform. They are independent of programming languages. An algorithm must have the following characteristics:

  • Input: An algorithm must have well-defined input. It can be 0 or more inputs.
  • Output: An algorithm must have well-defined output. It must match the desired output.
  • Precision: All steps are precisely defined.
  • Finiteness: An algorithm must stop after a certain number of steps. It should not run indefinitely.
  • Unambiguous: An algorithm should be clear and should not have any ambiguity in any of the steps.
  • Independent: An algorithm should be independent of any programming language or platforms.

Let us now create an algorithm. But in order to do that, we need a problem statement. So let us assume that we have a new shipment of books for our library. There are 1000 books and they are not sorted in any particular order. We need to find books as per the list and store them in their designated shelves. How do we find them from the pile of books?

Now, we can solve the problem in different ways. Each way has a different approach to find out a solution for the problem. We call these approaches algorithms. To keep the discussion short and precise, we are going to only consider two approaches to solve the problem. We know there are several other ways as well but for simplicity let us keep our discussion only for one algorithm.

We are going to store the books in a simple row so that we can see the book names. Now, we will pick a book name from the list and search from one end of the row to the other end till we find the book. So basically, we are going to follow a sequential search for each of the books. We will repeat these steps until we place all books in their designated places.

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