Exploring the complexity of PHP array deduplication algorithms

Complexity of PHP array deduplication algorithm: array_unique(): O(n)array_flip() array_keys(): O(n)foreach loop: O(n^2)

Explore the complexity of PHP array deduplication algorithm

Introduction

In PHP, array deduplication is a common operate. There are several different algorithms that can be used to do this, each with its own complexity. This article will explore the complexity of the most common array deduplication algorithms in PHP.

Array deduplication algorithm

In PHP, there are a variety of array deduplication algorithms to choose from, including:

• array_unique(): Built-in PHP function, implemented using hash table, complexity is O(n)
• array_flip() array_keys(): One uses hash table and solution for array inversion, complexity is O(n)
• foreach loop: Use nested loops to compare array elements and remove duplicates manually, complexity is O(n ^2)

Practical case

The following is a practical case for removing duplicates from a string array:

<?php
// 输入数组
$inputArray = ["a", "b", "c", "a", "d", "e", "c"];

// 使用 array_unique() 去重
$uniqueArray = array_unique($inputArray);

// 输出去重后的数组
print_r($uniqueArray);
?>

Complexity

##array_flip() array_keys()O(n) foreach loopO(n^2)

Algorithm	Complexity
array_unique()	O(n)

As shown in the above table, array_unique() and array_flip() array_keys() are both in O(n) Complete array deduplication within time complexity. This means that when the array is larger, the performance overhead of these two algorithms is also larger. On the other hand, the foreach loop has a complexity of O(n^2), which means that its performance overhead increases dramatically as the array size increases.

Choose the best algorithm

Choosing the best array deduplication algorithm depends on the array size and expected performance overhead. For smaller arrays, a foreach loop may be an acceptable choice. However, for larger arrays, array_unique() or array_flip() array_keys() will provide better performance.

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