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/**

* 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 BinaryTreePaths257 {

public List<String> binaryTreePaths(TreeNode root) {

List<String> res = new ArrayList<>();

binaryTreePaths(root, new StringBuilder(), res);

return res;

}

public void binaryTreePaths(TreeNode root, StringBuilder path, List<String> res) {

if (root == null) return;

path.append(root.val);

if (root.left == null && root.right == null) {

res.add(path.toString());

return;

}

path.append("->");

int l = path.length();

binaryTreePaths(root.left, path, res);

path.delete(l, path.length());

binaryTreePaths(root.right, path, res);

path.delete(l, path.length());

}

/**

* https://leetcode.com/problems/binary-tree-paths/discuss/68278/My-Java-solution-in-DFS-BFS-recursion

*/

public List<String> binaryTreePaths2(TreeNode root) {

List<String> sList=new LinkedList<String>();

if (root==null) return sList;

if (root.left==null && root.right==null) {

sList.add(Integer.toString(root.val));

return sList;

}

for (String s: binaryTreePaths(root.left)) {

sList.add(Integer.toString(root.val)+"->"+s);

}

for (String s: binaryTreePaths(root.right)) {

sList.add(Integer.toString(root.val)+"->"+s);

}

return sList;

}

}