1 
     data = $a[0];15 16         for ($i = 1; $i < count($a); $i++) {17             $node = new Node();18             $node->data = $a[$i];19             insert_node($root, $node);20         }        21 22         return $root;23     }24 25     #插入完全二叉树节点26     function insert_node($root, $inode) {27         #使用树的广度优先遍历顺序取出节点，直到找到第一个左右子节点没满的节点，将待插入节点插入节点左边或右边28         $queue = array();29         array_unshift($queue, $root);30 31         while (!empty($queue)) {32             $cnode = array_pop($queue);33             if ($cnode->left == null) {34                 $cnode->left = $inode;35                 $inode->parent = $cnode;36                 return $root;37             } else {38                 array_unshift($queue, $cnode->left);                39             }40             if ($cnode->right == null) {41                 $cnode->right = $inode;42                 $inode->parent = $cnode;43                 return $root;44             } else {45                 array_unshift($queue, $cnode->right);46             }47         }48 49         return $root;50     }51 52     #树的广度优先遍历 53     function bf_traverse($root) {54         $queue = array();55         array_unshift($queue, $root);56 57         while (!empty($queue)) {58             $cnode = array_pop($queue);59             echo $cnode->data . " ";60             if ($cnode->left !== null) array_unshift($queue, $cnode->left);61             if ($cnode->right !== null) array_unshift($queue, $cnode->right);62         }63 64         echo "
";65     }66 67     function get_paths($root, $paths, $sum) {68         if ($root != null) {69             $sum -= $root->data;70             $paths[] = $root->data;71 72             if ($sum > 0) {73                 #继续递归74                 #此处paths是传值调用，所以可以算出多条路径而互不影响75                 if ($root->left != null) get_paths($root->left, $paths, $sum);76                 if ($root->right != null) get_paths($root->right, $paths, $sum);77             } else if ($sum == 0) {78                 #输出路径79                 foreach ($paths as $val) {80                     echo $val . " ";81                 }82                 echo "
";83             }84         }85     }86 87     $a = array(9, 8, 7, 6, 8, 4, 3, 2, 1);88     $root = build_cbtree($a);89     bf_traverse($root); #广度优先遍历90     $b = array();91     get_paths($root, $b, 25); #输出路径和为25的路径92 ?>

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