标签：data enter ima 不能 [] null col after root
1、基本概念
二叉树每个节点最多有两个子树的结构，通常被称为“左子树”和“右子树”。
2、满二叉树
每个节点必须有两个子树，并且叶节点在同一层。
3、完全二叉树
节点的标记就是节点的值，意思就是节点的值是连续的，从左到右不能断裂，必须连续；
1、前序遍历：根节点-》左子树-》右子树
原则：先从根节点访问到左子树的低端，然后在访问右边（每一个子树又是一个二叉树）
程序：
//前序遍历二叉树：根节点-》左节点-》右节点
function preOrder($root)
{
$stack = [];
array_push($stack, $root);
while (!empty($stack)) {
$center_node = array_pop($stack);
echo $center_node->data.‘ ‘;
if($center_node->right != null) array_push($stack, $center_node->right);//右子树先入栈
if($center_node->left != null) array_push($stack, $center_node->left);
}
}
2、中序：根节点左子树-》根节点-》右子树
程序：
//中序遍历二叉树：左节点-》根节点-》右节点
function mindOrder($root)
{
$stack = [];
$center_node = $root;
while(!empty($stack) || $center_node != null){
while ($center_node != null) {
array_push($stack, $center_node);
$center_node = $center_node->left;
}
$center_node = array_pop($stack);
echo $center_node->data.‘ ‘;
$center_node = $center_node->right;
}
}
3、后序：左子树-》右子树-》根节点
程序：
//后序遍历二叉树：左节点-》右节点-》根节点
function afterOrder($root)
{
$stack = [];
$outStack = [];
array_push($stack, $root);
while(!empty($stack)){
$center_node = array_pop($stack);
array_push($outStack, $center_node);
if($center_node->left!=null)array_push($stack, $center_node->left);
if($center_node->right!=null)array_push($stack, $center_node->right);
}
while (!empty($outStack)){
$center_node= array_pop($outStack);
echo $center_node->data." ";
}
}
<?php
class Node{
public $left;
public $data;
public $right;
}
//前序遍历二叉树：根节点-》左节点-》右节点
function preOrder($root)
{
$stack = [];
array_push($stack, $root);
while (!empty($stack)) {
$center_node = array_pop($stack);
echo $center_node->data.‘ ‘;
if($center_node->right != null) array_push($stack, $center_node->right);//右子树先入栈
if($center_node->left != null) array_push($stack, $center_node->left);
}
}
//中序遍历二叉树：左节点-》根节点-》右节点
function mindOrder($root)
{
$stack = [];
$center_node = $root;
while(!empty($stack) || $center_node != null){
while ($center_node != null) {
array_push($stack, $center_node);
$center_node = $center_node->left;
}
$center_node = array_pop($stack);
echo $center_node->data.‘ ‘;
$center_node = $center_node->right;
}
}
//后序遍历二叉树：左节点-》右节点-》根节点
function afterOrder($root)
{
$stack = [];
$outStack = [];
array_push($stack, $root);
while(!empty($stack)){
$center_node = array_pop($stack);
array_push($outStack, $center_node);
if($center_node->left!=null)array_push($stack, $center_node->left);
if($center_node->right!=null)array_push($stack, $center_node->right);
}
while (!empty($outStack)){
$center_node= array_pop($outStack);
echo $center_node->data." ";
}
}
$a=new Node();
$b=new Node();
$c=new Node();
$d=new Node();
$e=new Node();
$f=new Node();
$h=new Node();
$k=new Node();
$m=new Node();
$a->data=1;
$b->data=2;
$c->data=3;
$d->data=4;
$e->data=5;
$f->data=6;
$h->data=7;
$k->data=8;
$m->data=9;
$a->left=$b;
$a->right=$c;
$b->left=$d;
$b->right=$e;
$c->left=$f;
$c->right=$h;
$d->left = $k;
$h->right = $m;
mindOrder($a);
标签：data enter ima 不能 [] null col after root
原文地址：https://www.cnblogs.com/meichao/p/9237370.html
