Shulou(Shulou.com)06/03 Report--

In this issue, the editor will bring you an example analysis of the array of sequential tables in the PHP data structure. The article is rich in content and analyzed and described from a professional point of view. I hope you can get something after reading this article.

PHP data structure-related logical operations of sequential tables (arrays)

After defining the physical structure, that is, the storage structure, we need to perform a series of logical operations on the storage structure. Here, we'll start with the sequence table, because the structure is very simple, which is our most commonly used array. So what do we usually do with arrays?

You don't have to think too complicated, all we need is these simple operations:

1. Find 2. Insert 3. Delete

Isn't it easy? Why isn't it traversed? Do we often have to traverse an array?

Note that here, we are ordering the physical structure of the table from a data structure point of view. Traversal operations are generally aimed at more complex structures, such as trees, graphs, traversing all paths starting from a node, and so on. As for the physical structure of the sequence table, we only need to master the above three operations and do not need to include traversal.

Another classmate said, in PHP, these three operations are simply too simple, there is no technical content at all!

Be careful not to enter the pit, look for what we are talking about is to find the subscript where this value is located, not to give you a subscript to simply output a value. In addition, insert and delete we need to consider a question, that is, after we insert or delete data in the first location, will iComple1 and its subsequent data be moved accordingly? Be careful, we are inserting and deleting the content of a subscript location, not modifying and replacing the content of this subscript!

All right, let's just illustrate it with an example.

Insert / * *

* Array insertion

* @ param array $list order table array

* @ param int $I insert data subscript

* @ param mixed $e array elements

* result of success and failure of return bool

, /

Function ListInsert (array & $list, int $I, $e)

{

C = count ($list)

If ($I

< 0 || $i >

$c) {

Return false

}

$j = $c-1

While ($j > = $I) {

/ / from back to front, the value of the next position becomes the value of the present position

/ / data is moved backwards

$list [$j + 1] = $list [$j]

$jmurt-

}

/ / insert a value at the specified location

$list [$I] = $e

Return true

}

The insertion operation first determines whether the subscript is out of bounds. Next, the data after the insertion position is moved back one bit from back to front, and finally the newly added data is placed in the specified location. It is important to note that in this operation, our main concern is the movement of the data location. Why should we move from the last bit of the array instead of from the insertion position? If you start from the insertion position, then the following data will be the same data, that is, the next data at the insertion location. If you are interested, you can try it yourself.

Arr = [1, 2, 3, 4, 5, 6, 7]

ListInsert ($arr, 3,55)

Print_r ($arr)

/ / Array

/ / (

/ / [0] = > 1

/ / [1] = > 2

/ / [2] = > 3

/ / [3] = > 55

/ / [4] = > 4

/ / [5] = > 5

/ / [6] = > 6

/ / [7] = > 7

/ /)

In the above test code, we insert a data 55 into position 3 of the data. As you can see from the output, the length of the array has increased by one bit, and the subsequent data has been moved backward one bit since the position of subscript 3.

Delete / * *

* Delete the specified subscript element

* @ param array $list order table array

* @ param int $I insert data subscript

* result of success and failure of return bool

, /

Function ListDelete (array & $list, int $I)

{

C = count ($list)

If ($I

< 0 || $i >

$c-1) {

Return false

}

$j = $I

While ($j

< $c) { // 当前位置的值变成下一个位置的值 // 数据向前挪动 $list[$j] = $list[$j+1]; $j++; } // 去掉最后一个数据 unset($list[$c - 1]); return true; } 学习了上面的插入操作之后，相信大部分同学也能想象到删除元素的操作正好跟插入是返过来的。第一步依然还是判断下标是否合规。接下来就是把指定删除的下标元素之后的元素向前挪动一位。在这里，我们是从删除下标开始将元素依次向前移动一位，最后再删除掉重复的最后一位数据，也就是实现数组元素数量的减 1 操作。 $arr = [1, 2, 3, 4, 5, 6, 7]; ListDelete($arr, 5); print_r($arr); // Array // ( // [0] =>

one

/ / [1] = > 2

/ / [2] = > 3

/ / [3] = > 4

/ / [4] = > 5

/ / [5] = > 7

/ /)

The test results are also clear that the original element at subscript 5 is 6. After we delete the element with subscript 5, the number of elements in the whole data is reduced by one bit, and the following elements are moved up, that is, element 7 is moved to the position of 5.

Find

Search is simply to do a linear search, that is, to compare the data one by one to see where the data we need is in the array.

/ * *

* find

* @ param array $list order table array

* @ param mixed $e array elements

* return int search result subscript

, /

Function LocateElem (array $list, $e)

{

C = count ($list)

For ($I = 0; $I < $c; $iTunes +) {

If ($list [$I] = = $e) {

Return $I

}

}

Return-1

}

If we find the data, we return the subscript of the location of the current data. If the corresponding data is not found in the end, a-1 is returned to indicate that we have not found the corresponding data.

Summary

Welcome to the world of data structures and algorithms. I'm not surprised or surprised. I wrote so much code for the first time today, but does it feel different from what we usually write? Just like inserting and deleting data movement, if you don't pay attention to it, you may not really know that we should move the other way to get the right results. This is the fun of data structure and algorithm learning, challenge yourself, every day is beyond!

Test the code:

Https://github.com/zhangyue0503/Data-structure-and-algorithm/blob/master/2. Linear table / source/2.2%20 sequence table (array)

The above is an example of an array of sequential tables in the PHP data structure shared by the editor. If you happen to have similar doubts, you might as well refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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