PHP array key and value interchange: efficiency comparison of different algorithms

In PHP, the best algorithm for exchanging array keys and values ​​is: array_flip(): time complexity O(n), space complexity O(n). foreach() loop: suitable for large arrays, time complexity O(n), space complexity O(1). array_combine(): similar to array_flip(), but with a custom key-value array, time complexity O(n), space complexity O(2n).

PHP Array Key and Value Interchange: Efficiency Comparison of Different Algorithms

Introduction

In PHP, you may encounter scenarios where you need to exchange array keys and values. There are multiple algorithms for doing this, each with its own efficiency characteristics. This article will compare the efficiency of different algorithms and provide a practical case.

Algorithm

• ##array_flip(): Built-in function, the array key is used as the value of the new array, and the value is used as the value of the new array key.
• foreach() loop: Use a loop to traverse the array, use temporary variables to temporarily store the keys and values, and then exchange them.
• array_combine(): Similar to array_flip(), but allows custom key and value arrays.

Efficiency comparison

The following table compares the efficiency of different algorithms:

AlgorithmTime complexitySpace complexityarray_flip()O(n)O(n)foreach() loopO(n)O(1)array_combine()O(n)O(2n)##Practical case

Consider the following array:

$array = ['foo' => 1, 'bar' => 2, 'baz' => 3];

We can use the array_flip() function to interchange the keys and values:

$newArray = array_flip($array);

The result is as follows:

$newArray = [1 => 'foo', 2 => 'bar', 3 => 'baz'];

Conclusion

In most cases, the array_flip() function is the best choice for swapping array keys and values ​​because it has minimal space complexity and constant time complexity. For very large arrays, a foreach() loop may be more efficient because it has a smaller memory consumption.

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