剑指 Offer 34. 二叉树中和为某一值的路径

剑指 Offer 34. 二叉树中和为某一值的路径

难度中等

输入一棵二叉树和一个整数,打印出二叉树中节点值的和为输入整数的所有路径。从树的根节点开始往下一直到叶节点所经过的节点形成一条路径。

示例:

给定如下二叉树,以及目标和 target = 22,

5

/ \

4 8

/ / \

11 13 4

/ \ / \

7 2 5 1

返回:

[

[5,4,11,2],

[5,8,4,5]

]

提示:

  1. 节点总数 <= 10000

注意:本题与主站 113 题相同:https://leetcode-cn.com/problems/path-sum-ii/

/**

* Definition for a binary tree node.

* public class TreeNode {

*     int val;

*     TreeNode left;

*     TreeNode right;

*     TreeNode() {}

*     TreeNode(int val) { this.val = val; }

*     TreeNode(int val, TreeNode left, TreeNode right) {

*         this.val = val;

*         this.left = left;

*         this.right = right;

*     }

* }

*/

class Solution {

        List<List<Integer>> ret = new ArrayList<>();

        public List<List<Integer>> pathSum(TreeNode root, int target) {

            dfs(new ArrayList<>(),root,target);

            return ret;

        }

        private void dfs(ArrayList<Integer> list, TreeNode root, int target) {

            if (root == null){

                return;

            }

            list.add(root.val);

            target-=root.val;

            if (0==target&&root.left == null &&root.right == null){

                ret.add(new ArrayList<>(list));

            }else{

                dfs(list,root.left,target);

                dfs(list,root.right,target);

            }

            list.remove(list.size()-1);

        }

}

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