php Realizes Path Method with Sum as a Value in Binary Tree

A path in a 2-tree where the sum is a value of 1:

Enter a heel node of a 2-tree and an integer, and print out all paths where the sum of node values in the 2-tree is the input integer. The path is defined as a path from the root node of the tree down 1 to the node through which the leaf node passes to form 1 path. (Note: In the list of the return value, the array with large array length comes first.)

Thoughts:

Pre-order traversal of 1, 2-tree, middle left and right order

2. Pass in the target value target, target-=val

3. target is 0 and left and right are null, reaching the leaf node

4. Two arrays outside the function, list array stores one path and listAll array stores all paths

FindPath(root,target)

  if root==null return listAll

  list[]=root.val

  target-=root.val

  if target==0 && root->left==null && root->right==null

    listAll[]=list

  FindPath(root->left,target)

  FindPath(root->right,target)

  // If you reach the following node of this path and fail to achieve the goal, delete the last node and return to the upper node 1 Node 

  array_pop(list)

  return listAll

<?php

class TreeNode{

  var $val;

  var $left = NULL;

  var $right = NULL;

  function __construct($val){

    $this->val = $val;

  }  

}

 

function FindPath($root,$target)

{

    static $list=array();

    static $listAll=array();

    if($root==null){

        return $listAll;

    }  

    $target-=$root->val;

    $list[]=$root->val;

    if($target==0 && $root->left==null && $root->right==null){

        $listAll[]=$list;

    }  

    FindPath($root->left,$target);

    FindPath($root->right,$target);

    array_pop($list);

    return $listAll;

}

 

$node10=new TreeNode(10);

$node5=new TreeNode(5);

$node12=new TreeNode(12);

$node4=new TreeNode(4);

$node7=new TreeNode(7);

 

$node10->left=$node5;

$node10->right=$node12;

$node5->left=$node4;

$node5->left=$node7;

 

$tree=$node10;

 

$res=FindPath($tree,22);

var_dump($res);

<?php

/*class TreeNode{

  var $val;

  var $left = NULL;

  var $right = NULL;

  function __construct($val){

    $this->val = $val;

  }

}*/

function FindPath($root,$target)

{

  $list=array();

  $listAll=array();

  $res=dfs($root,$target,$list,$listAll);

  return $res;

}

 

function dfs($root,$target,&$list,&$listAll)

{

 

    if($root==null){

        return $listAll;

    }  

    $target-=$root->val;

    $list[]=$root->val;

    if($target==0 && $root->left==null && $root->right==null){

         

        $listAll[]=$list;

    }  

    dfs($root->left,$target,$list,$listAll);

    dfs($root->right,$target,$list,$listAll);

    array_pop($list);

    return $listAll;

}

The above is the content of all examples of the code, you can test 1, thank you for the support of this site.