Leetcode:Path Sum II

url:

https://leetcode.com/problems/path-sum-ii/description/

描述：

Given a binary tree and a sum, find all root-to-leaf paths where each path’s sum equals the given sum.
For example:
Given the below binary tree and sum = 22,

          5         / \        4   8       /   / \      11  13  4     /  \    / \    7    2  5   1

return

[
[5,4,11,2],
[5,8,4,5]
]

解题思路：

深度优先搜索

示例代码：

class Solution {    private List<List<Integer>> res = new ArrayList();    public List<List<Integer>> pathSum(TreeNode root, int sum) {        dfs(sum,root,new ArrayList<Integer>());        return res;    }    private void dfs(int sum,TreeNode root,List<Integer> temp){        if(root==null) return;        if(sum-root.val==0&&root.left==null&&root.right==null){            temp.add(root.val);            res.add(new ArrayList(temp));        }else if(sum>0||root!=null){            temp.add(root.val);            dfs(sum-root.val,root.left,temp);            dfs(sum-root.val,root.right,temp);        }        temp.remove(temp.size()-1);    }}