前言
最近接到一個關於樹的需求，想起了大學那會兒聽過俞敏洪有關樹的演講，老師重複在課上放了很多次，N年過去了印象還是很深。
演講內容是介樣的，讓我們一起來喝湯~
人的生活方式有兩種，
第一種方式是像草一樣活著，
你儘管活著，
每年還在成長，
但是你畢竟是一棵草，
你吸收雨露陽光，
但是卻長不大。
人們可以踩過你，
但是人們不會因為你的痛苦，而他產生痛苦；
人們不會因為你被踩了，而來憐憫你，
因為人們本身就沒有看到你。
所以我們每一個人，
都應該像樹一樣的成長，
即使我們現在什麼都不是，
但是隻要你有樹的種子，
即使你被踩到泥土中間，
你依然能夠吸收泥土的養分，
自己成長起來。
當你長成參天大樹以後，
遙遠的地方，人們就能看到你；
走近你，你能給人一片綠色。
活著是美麗的風景，
死了依然是棟樑之才，
活著死了都有用。
回到今天的主題，需求是這樣的：構造無限級樹型結構，介面類似下邊這樣的結構
然後，還需要把所有的橙色標記的葉子節點從垂直方向篩選出來，最終效果就是得到一個這樣順序的一級陣列
KKK
QQQ
JJJ
HHH
GGG
LLL
需要根據AAA這個節點和他所有子節點的資料，構造出一個無限級樹型結構，如下
資料
- 頂級AAA資料
{"id":348019,"name":"AAA","is_leaf":2,"parent_id":347234,"type":0,"order":["348020"]}
- AAA所有的孩子節點
[{"id":348020,"name":"BBB","is_leaf":2,"parent_id":348019,"type":0,"order":["348037","348033","348021","348023","348034"]},{"id":348021,"name":"CCC","is_leaf":2,"parent_id":348020,"type":0,"order":["348022","348035"]},{"id":348022,"name":"DDD","is_leaf":2,"parent_id":348021,"type":0,"order":["348024","348032","348030"]},{"id":348024,"name":"EEE","is_leaf":2,"parent_id":348022,"type":0,"order":["348025","348036"]},{"id":348025,"name":"FFF","is_leaf":2,"parent_id":348024,"type":0,"order":["348031"]},{"id":348030,"name":"HHH","is_leaf":1,"parent_id":348022,"type":11,"order":[]},{"id":348023,"name":"GGG","is_leaf":1,"parent_id":348020,"type":11,"order":[]},{"id":348031,"name":"QQQ","is_leaf":1,"parent_id":348025,"type":11,"order":[]},{"id":348032,"name":"JJJ","is_leaf":1,"parent_id":348022,"type":11,"order":[]},{"id":348035,"name":"MMM\u65e0\u53f6\u5b50","is_leaf":2,"parent_id":348021,"type":0,"order":[]},{"id":348036,"name":"NNN\u65e0\u53f6\u5b50","is_leaf":2,"parent_id":348024,"type":0,"order":[]},{"id":348033,"name":"KKK","is_leaf":1,"parent_id":348020,"type":11,"order":[]},{"id":348037,"name":"OOO","is_leaf":2,"parent_id":348020,"type":0,"order":[]},{"id":348034,"name":"LLL","is_leaf":1,"parent_id":348020,"type":11,"order":[]}]
節點資料庫結構都一樣，核心是有一個parent_id，每個節點會儲存直屬葉子的排序order
實現
其實這裡考察的遞迴構造樹、廣度優先遍歷、深度優先遍歷
其實不管啥語言，思想都是這樣，因為這個需求是php系統寫的介面，就用php給出實現程式碼，氣氛搞起來~
構造無限級
private function getTree($list, $node)
{
$tree = [];
foreach ($list as $k => $v) {
if ($v['parent_id'] == $node['id']) {
$v['children'] = $this->getTree($list, $v);
$tree[] = $v;
}
}
if (empty($node['order'])) {
return [];
}
//注意：為了保證所有的葉子節點是根據已有的order排序，這裡我們重新擺放一下
$treeMap = [];
foreach ($tree as $v) {
$treeMap[$v['id']] = $v;//建立id和資料的map
}
//根據order重新排序
$orderTree = [];
foreach ($node['order'] as $id) {//根據order的順序重新擺放
$orderTree[] = $treeMap[$id];
}
return $orderTree;
}
我們來使用一下，使用如下
最終輸出的json如下
可以看到，已經構造出了一個無限級的樹，並且和我們的介面是一模一樣的層級和順序
拉下來現在我們要遍歷這棵樹，為了獲取到所有is_leaft=1的節點，我們先用廣度優先遍歷來試一下，因為這個對於找節點來說效能比較高
廣度優先遍歷
程式碼如下
private function bfsFindLeafs($node)
{
$result = [];//滿足條件的組合
$q = [];
$q[] = $node;
while (count($q) > 0) {
$size = count($q);
for ($i = 0; $i < $size; $i++) {
$current = array_pop($q);
//判斷節點如果是滿足條件，加入路徑
if ($current['is_leaf'] == 1) {
$result[] = $current;
}
//把所有的子節點加入佇列
foreach ($current['children'] as $v) {
$q[] = $v;
}
}
}
return $result;
}
我們來使用一下
$getAllLeafs = $this->bfsFindLeafs($topNode);
echo json_encode($getAllLeafs);
執行後輸出
[
{
"id": 348034,
"name": "LLL",
"is_leaf": 1,
"parent_id": 348020,
"type": 11,
"order": [],
"children": []
},
{
"id": 348023,
"name": "GGG",
"is_leaf": 1,
"parent_id": 348020,
"type": 11,
"order": [],
"children": []
},
{
"id": 348030,
"name": "HHH",
"is_leaf": 1,
"parent_id": 348022,
"type": 11,
"order": [],
"children": []
},
{
"id": 348032,
"name": "JJJ",
"is_leaf": 1,
"parent_id": 348022,
"type": 11,
"order": [],
"children": []
},
{
"id": 348031,
"name": "QQQ",
"is_leaf": 1,
"parent_id": 348025,
"type": 11,
"order": [],
"children": []
},
{
"id": 348033,
"name": "KKK",
"is_leaf": 1,
"parent_id": 348020,
"type": 11,
"order": [],
"children": []
}
]
好，我們已經可以獲取到所有is_leaf為1的節點了，但是這裡有一個問題，不是從上到下輸出的
LLL
GGG
HHH
JJJ
QQQ
KKK
這時候，我們就需要一個深度優先遍歷來實現了
深度優先遍歷
深度優先遍歷其實就是回滾演算法的一種，為了從上到下輸出，需要先序遍歷
private function dfsFindLeafs($node)
{
$trackList = [];
foreach ($node['children'] as $v) {
if ($v['is_leaf'] == 1) {
$trackList[] = $v;
}
if (empty($v['children'])) {
continue;
}
$trackList = array_merge($trackList,$this->dfsFindLeafs($v));
}
return $trackList;
}
我們再來執行一下
$getAllLeafs = $this->dfsFindLeafs($topNode);
echo json_encode($getAllLeafs);
輸出
[
{
"id": 348033,
"name": "KKK",
"is_leaf": 1,
"parent_id": 348020,
"type": 11,
"order": [],
"children": []
},
{
"id": 348031,
"name": "QQQ",
"is_leaf": 1,
"parent_id": 348025,
"type": 11,
"order": [],
"children": []
},
{
"id": 348032,
"name": "JJJ",
"is_leaf": 1,
"parent_id": 348022,
"type": 11,
"order": [],
"children": []
},
{
"id": 348030,
"name": "HHH",
"is_leaf": 1,
"parent_id": 348022,
"type": 11,
"order": [],
"children": []
},
{
"id": 348023,
"name": "GGG",
"is_leaf": 1,
"parent_id": 348020,
"type": 11,
"order": [],
"children": []
},
{
"id": 348034,
"name": "LLL",
"is_leaf": 1,
"parent_id": 348020,
"type": 11,
"order": [],
"children": []
}
]
順序為
KKK
QQQ
JJJ
HHH
GGG
LLL
這次順序終於對了，oh yeah~，和我們之前的介面垂直順序一致
完整程式碼
下面給出完整程式碼
<?php
/**
* Class Test
* @author chenqionghe
*/
class Test
{
public function run()
{
$topNodeJson = '{"id":348019,"name":"AAA","is_leaf":2,"parent_id":347234,"type":0,"order":["348020"]}';
$childrenJson = '[{"id":348020,"name":"BBB","is_leaf":2,"parent_id":348019,"type":0,"order":["348037","348033","348021","348023","348034"]},{"id":348021,"name":"CCC","is_leaf":2,"parent_id":348020,"type":0,"order":["348022","348035"]},{"id":348022,"name":"DDD","is_leaf":2,"parent_id":348021,"type":0,"order":["348024","348032","348030"]},{"id":348024,"name":"EEE","is_leaf":2,"parent_id":348022,"type":0,"order":["348025","348036"]},{"id":348025,"name":"FFF","is_leaf":2,"parent_id":348024,"type":0,"order":["348031"]},{"id":348030,"name":"HHH","is_leaf":1,"parent_id":348022,"type":11,"order":[]},{"id":348023,"name":"GGG","is_leaf":1,"parent_id":348020,"type":11,"order":[]},{"id":348031,"name":"QQQ","is_leaf":1,"parent_id":348025,"type":11,"order":[]},{"id":348032,"name":"JJJ","is_leaf":1,"parent_id":348022,"type":11,"order":[]},{"id":348035,"name":"MMM\u65e0\u53f6\u5b50","is_leaf":2,"parent_id":348021,"type":0,"order":[]},{"id":348036,"name":"NNN\u65e0\u53f6\u5b50","is_leaf":2,"parent_id":348024,"type":0,"order":[]},{"id":348033,"name":"KKK","is_leaf":1,"parent_id":348020,"type":11,"order":[]},{"id":348037,"name":"OOO","is_leaf":2,"parent_id":348020,"type":0,"order":[]},{"id":348034,"name":"LLL","is_leaf":1,"parent_id":348020,"type":11,"order":[]}]';
$topNode = json_decode($topNodeJson, true);
$childrenList = json_decode($childrenJson, true);
$topNode['children'] = $this->getTree($childrenList, $topNode);
$getAllLeafs = $this->dfsFindLeafs($topNode);
echo json_encode($getAllLeafs);
}
/**
* 遞迴構造無限級樹
*
* @param $list
* @param $node
* @return array
*/
private function getTree($list, $node)
{
$tree = [];
foreach ($list as $k => $v) {
if ($v['parent_id'] == $node['id']) {
$v['children'] = $this->getTree($list, $v);
$tree[] = $v;
}
}
if (empty($node['order'])) {
return [];
}
//注意：為了保證所有的葉子節點是根據已有的order排序，這裡我們重新擺放一下
$treeMap = [];
foreach ($tree as $v) {
$treeMap[$v['id']] = $v;//建立id和資料的map
}
//根據order重新排序
$orderTree = [];
foreach ($node['order'] as $id) {//根據order的順序重新擺放
$orderTree[] = $treeMap[$id];
}
return $orderTree;
}
/**
* 廣度優先遍歷獲取所有葉子
* @param $node
* @return array
*/
private function bfsFindLeafs($node)
{
$result = [];//滿足條件的組合
$q = [];
$q[] = $node;
while (count($q) > 0) {
$size = count($q);
for ($i = 0; $i < $size; $i++) {
$current = array_pop($q);
//判斷節點如果是滿足條件，加入路徑
if ($current['is_leaf'] == 1) {
$result[] = $current;
}
//把所有的子節點加入佇列
foreach ($current['children'] as $v) {
$q[] = $v;
}
}
}
return $result;
}
/**
* 獲取所有的葉子路徑（深度度優先遍歷）
*/
private function dfsFindLeafs($node)
{
$trackList = [];
foreach ($node['children'] as $v) {
if ($v['is_leaf'] == 1) {
$trackList[] = $v;
}
if (empty($v['children'])) {
continue;
}
$trackList = array_merge($trackList, $this->dfsFindLeafs($v));
}
return $trackList;
}
}
(new Test())->run();
ok，到這裡我們就已經學會如何構造無限級樹型結構，並學會用深度優先遍歷垂直輸出指定條件節點，還知道了怎麼用廣度優先遍歷，giao~