[leetcode]Path Sum II

Path Sum II

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]
]

算法思路：

跟[leetcode]Path Sum区别不大，dfs

代码如下：

 1 public class Solution {
 2     List<List<Integer>> res = new ArrayList<List<Integer>>();
 3     public List<List<Integer>> pathSum(TreeNode root, int sum) {
 4         if(root == null) return res;
 5         List<Integer> list = new ArrayList<Integer>();
 6         dfs(list, root, sum);
 7         return res;
 8     }
 9     public void dfs(List<Integer> list,TreeNode root,int sum){
10         if(root.left == null && root.right == null && root.val == sum){
11             list.add(sum);
12             res.add(new ArrayList<Integer>(list));
13             list.remove(list.size() - 1);
14             return;
15         }
16         if(root.left != null){
17             list.add(root.val);
18             dfs(list, root.left, sum - root.val);
19             list.remove(list.size() - 1);
20         }
21         if(root.right!= null){
22             list.add(root.val);
23             dfs(list, root.right, sum - root.val);
24             list.remove(list.size() - 1);
25         }
26     }
27 }