Data structure and algorithm improvement skills in Java

Java is a widely used programming language, not only suitable for large-scale enterprise-level applications, but also for small-scale application and game development. It is very important for Java developers to master data structure and algorithm skills, because these skills can help developers improve the performance and stability of their programs. In this article, we will introduce several data structures and algorithm techniques commonly used in Java programs and how to use them to improve the efficiency of your code.

1. Arrays and linked lists

Arrays and linked lists in Java are two commonly used data structures. An array is an ordered, fixed-size collection of data whose elements are accessed through subscripts. A linked list is a data structure consisting of nodes, each node containing data and a pointer to the next node. In contrast, linked lists are more dynamic and flexible because nodes can be inserted or deleted as needed without reallocating memory space.

When you need to quickly access elements in an array, you can use the binary search algorithm to achieve it. The time complexity of this algorithm is O(log n), which is better than the time complexity of the linear search algorithm, O(n). But this algorithm only works on sorted arrays. In contrast, the most commonly used algorithm for linked lists is traversal, which has a time complexity of O(n). But due to the dynamic nature of the linked list, data can be easily inserted or deleted in the linked list.

2. Heap, stack and queue

Heap, stack and queue are other commonly used data structures in Java. Heap is a binary tree-based data structure that can quickly find the maximum or minimum value. The stack is a last-in-first-out (LIFO) data structure commonly used in programs for function calls and memory allocation. A queue is a first-in, first-out (FIFO) data structure commonly used in event-driven programming.

Heap sorting is a classic algorithm that uses a heap to implement sorting, with a time complexity of O(nlog n). Stacks and queues also have many commonly used algorithms, such as depth-first search and breadth-first search. Depth-first search algorithms are implemented using recursion on a stack, while breadth-first search algorithms are implemented using loops on a queue.

3. Hash table

A hash table is a data structure based on a hash function that can be used to implement a collection of key-value pairs. Hash functions map keys to values ​​with a certain data structure, allowing data to be quickly found and accessed. The HashMap and HashSet data structures in Java are implemented based on hash tables.

The most commonly used algorithms for hash tables are hash lookup and hash conflict resolution. A hash lookup calculates the location of a key through a hash function and then performs a lookup at that location. Hash conflict resolution is to handle possible key conflicts in the hash table so that each key can be stored correctly in the hash table.

4. Sort algorithm

Sort algorithm is a very important type of algorithm that can be used to classify, search and analyze data. Commonly used sorting algorithms in Java include bubble sort, insertion sort, selection sort, merge sort and quick sort. Although the time complexity of these algorithms differs, they can all be used in Java programs to sort arrays and collections.

Merge sort and quick sort are one of the most commonly used sorting algorithms. Merge sort divides a data set into two sub-sets, sorts them separately, and then merges them into an ordered set. Quick sort uses a similar approach, but it uses randomly selected pivots to be faster than merge sort.

Summary

For Java developers, mastering data structure and algorithm skills is extremely important. This article introduces some commonly used data structures and algorithm techniques, including arrays, linked lists, heaps, stacks, queues, hash tables, and sorting algorithms. By knowing and deeply understanding these techniques, you can better write efficient Java programs.

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