[LeetCode]257. Binary Tree Paths

Given a binary tree, return all root-to-leaf paths.

For example, given the following binary tree:

   1 /   \2     3 \  5

All root-to-leaf paths are:

["1->2->5", "1->3"]

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    List<String> res = new ArrayList<>();        public List<String> binaryTreePaths(TreeNode root) {        String single = new String();                if(root==null) return res;                singlePath(root, root.val + "");        return res;    }        public void singlePath(TreeNode node, String single){        if(node.left==null && node.right==null)             res.add(single);                if(node.left!=null)             singlePath(node.left, single+"->"+node.left.val+"");                if(node.right!=null)             singlePath(node.right, single+"->"+node.right.val+"");    }}

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