无法在php中以遍历顺序显示所有树 [英] Can't get to show all of a tree in a traversal preorder in php

问题描述

我的数据库中有一个表，其中包含许多家谱树.

I have a table in my database that host many genealogy trees.

-----------------------------
- id  name              parent_id
-----------------------------
- 1   grandfather       NULL
- 2   father            1
- 3   uncle             1
- 4   son               2
- 5   brother           2
- 6   cousin's dauther  7
- 7   cousin            8
- 8   auntie            1

问题是由于出现边缘情况，我无法显示所有名称:

The problem is I can't get to show all the names because of an edge case:

-当我的某人的parent_id大于其父母的parent_id时 (请参阅表弟的女儿)

-When I have a person with a parent_id that is bigger than it's parent's parent_id (see cousin's daugter)

我使用以下查询获取表格:

I use this queries to get the table:

    $sql = "SELECT p1.id, p1.name, p1.parent_id FROM pariente p1 
    ORDER BY p1.parent_id";
    $result = $conn->query($sql);

问题是，如果我使用"ORDER BY parent_id"，表兄弟的dauther"将不会显示，如果我使用"ORDER BY id"，"cousin"将不会显示.

The problem is that if I use "ORDER BY parent_id" "cousin's dauther" won't show and if I use "ORDER BY id" "cousin" won't show.

我使用此功能将一棵树制成一个数组并绘制它:

I use this functions to make a the tree into an array and draw it:

        function make_tree($data, $root) {
            $tree = [];
            foreach ($data as $node) {
                insert($tree, $node);
            }

            return $tree;
        }

        function insert(&$root, &$node) {
            if (!$root) {
                $root = $node;
            }
            else if ($root["id"] === $node["parent_id"]) {
                $root["children"][] = $node;
            }
            else if (array_key_exists("children", $root)) {
                foreach ($root["children"] as &$c) {
                    if (insert($c, $node)) {
                        break;
                    }
                }
            }
        }

        function preorder2(&$root) {
            if ($root) {
                echo "<li>";
                echo $root["name"];

                if (array_key_exists("children", $root)) {
                    echo "<ul>";
                    foreach ($root["children"] as $c) {
                        preorder2($c);
                    }
                    echo "</ul>";
                }
                echo "</li>";
            }
        }
    ?>

然后我使用它来调用函数:

And after I use this to call the functions:

<div>

<?php
while( $row = mysqli_fetch_assoc( $result)){
    $resguard[] = $row;
}
    $tree = make_tree($resguard);
    preorder2($tree);
?>
</div>

推荐答案

我曾经遇到过类似的问题，下面是解决问题的方法.

I had a similar problem once, and here's how I fixed it.

1. 遍历数据集，将每个节点放入数组中，并跟踪要成为根节点的内容.

1. Iterate over the dataset, putting each node in your array, and keep track of what you want to be your root node.

遍历数组.对于parent_id不为null的每个节点，请按id查找父节点，然后将当前节点添加为子节点.构建树时无需使用递归.

Iterate over the array. For each node where the parent_id is not null, lookup the parent node by id, and add the current node as a child. There's no need to use recursion when building the tree.

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