题目描述：
给一棵二叉树，找出从根节点到叶子节点的所有路径。
样例：
给出下面这棵二叉树：
1
/ \
2 3
\
5
所有根到叶子的路径为：
[
"1->2->5",
"1->3"
]
代码实现：
/**
* Definition of TreeNode:
* public class TreeNode {
* public int val;
* public TreeNode left, right;
* public TreeNode(int val) {
* this.val = val;
* this.left = this.right = null;
* }
* }
*/
public class Solution {
/**
* @param root the root of the binary tree
* @return all root-to-leaf paths
*/
public List<String> binaryTreePaths(TreeNode root) {
List<String> paths = new ArrayList<>();
if (root == null) {
return paths;
}
//root is a leaf
if (root.left == null && root.right == null) {
paths.add(root.val + "");
}
List<String> leftPath = binaryTreePaths(root.left);
List<String> rightPath = binaryTreePaths(root.right);
for (String path : leftPath) {
paths.add(root.val + "->" + path);
}
for (String path : rightPath) {
paths.add(root.val + "->" + path);
}
return paths;
}
}
