[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：

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