package jiuzhang.java.elementary;

//Binary Tree Paths

import java.util.ArrayList;

import java.util.List;

public class BinaryTreePaths {

public List<String> binaryTreePaths(TreeNode root) {

// write your code here

if(root == null) {

return new ArrayList<String>();

}

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

ArrayList<String> aList = new ArrayList<String>();

aList.add(String.valueOf(root.val));

return aList ;

}

ArrayList<String> result = new ArrayList<String>(binaryTreePaths(root.left));

result.addAll(binaryTreePaths(root.right));

for (int i = 0; i < result.size(); i++) {

result.set(i, "" + root.val + "->" + result.get(i));

}

// cannot use this b/c path is a new ref to a new string(after operation), the original string is not changed

// this is the immutable property of string in java

// must use the object's own method to change itself

//

// for (String path: result) {

// StringBuilder sb = new StringBuilder(path);

// sb.insert(0, "->");

// sb.insert(0, root.val);

// path = sb.toString();

// System.out.println(path);

// }

//

// System.out.println("result: " + result);

return result;

}

public static void main(String[] args) {

// TODO Auto-generated method stub

TreeNode aRoot = new TreeNode(1);

aRoot.left = new TreeNode(2);

aRoot.right = new TreeNode(3);

aRoot.left.left = null;

aRoot.left.right = new TreeNode(5);

List<String> result = new BinaryTreePaths().binaryTreePaths(aRoot);

}

}