PHP遍历二叉树

 1 class Node {
 2     public $data = null;
 3     public $left = null;
 4     public $right = null;
 5 }
 6 
 7 $node1 = new Node();
 8 $node2 = new Node();
 9 $node3 = new Node();
10 $node4 = new Node();
11 $node5 = new Node();
12 $node6 = new Node();
13 $node7 = new Node();
14 $node8 = new Node();
15 $node9 = new Node();
16 
17 $node1->data = 1;
18 $node2->data = 2;
19 $node3->data = 3;
20 $node4->data = 4;
21 $node5->data = 5;
22 $node6->data = 6;
23 $node7->data = 7;
24 $node8->data = 8;
25 $node9->data = 9;
26 
27 $node1->left = $node2;
28 $node1->right = $node3;
29 $node2->left = $node4;
30 $node2->right = $node5;
31 $node3->left = $node6;
32 $node3->right = $node7;
33 $node4->left = $node8;
34 $node4->right = $node9;

 1 // 二叉树广度优先遍历
 2 function binary_tree1($node) {
 3     $result = [];//保存结果
 4     $memc = [];
 5     array_push($memc, $node);//根节点入队
 6     while (!empty($memc)) {//持续输出节点，直到队列为空
 7         $cnode = array_shift($memc);//最前边的元素出队
 8         $result[] = $cnode->data;//记录当前节点的值
 9         //左节点先入队，然后右节点入队
10         if ($cnode->left != null) 
11             array_push($memc, $cnode->left);
12         if ($cnode->right != null) 
13             array_push($memc, $cnode->right);
14     }
15     return $result;
16 }
17 
18 print_r(binary_tree2($node1));

 1 // 二叉树深度优先遍历（先序）
 2 function binary_tree2($node)
 3 {
 4     $result = [];//结果数组
 5     $memc  = [];
 6     array_push($memc, $node);//将根节点压栈
 7     while (!empty($memc)) {
 8         $cnode = array_pop($memc);//弹出刚刚压栈的节点
 9         $result[] = $cnode->data;
10         //因为先进后出原则，想先显示左子树，所以先压入右子树
11         if ($cnode->right != null) {
12             array_push($memc, $cnode->right);
13         }
14         if ($cnode->left != null) {
15             array_push($memc, $cnode->left);
16         }
17     }
18     return $result;
19 }
20 
21 print_r(binary_tree2($node1));