BinaryTreePaths.java

/*
 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"]
*/


import java.io.*;
import java.util.*;
public class BinaryTreePaths {
	public static class TreeNode {
		int val;
		TreeNode left;
		TreeNode right;
		TreeNode(int x) { val = x; }
	}
	
	public static List<String> res = new ArrayList<String>();

    public static List<String> binaryTreePaths(TreeNode root) {
        if(root == null) return res;
        goToL(root, "");
        return res;
    }
    
    public static void goToL(TreeNode p, String sp){
        if(p.left == null && p.right==null){
            res.add(sp + p.val);
            return;
        }
        if(p.left!=null) goToL(p.left, sp + p.val + "->");
        if(p.right != null) goToL(p.right, sp + p.val + "->");
        
    }
	public static void main(String[] args) { 
		TreeNode root = new TreeNode(1);
		TreeNode node2 = new TreeNode(2);
		TreeNode node3 = new TreeNode(3);
		TreeNode node4 = new TreeNode(4);
		TreeNode node5 = new TreeNode(5);
		TreeNode node6 = new TreeNode(6);
		TreeNode node7 = new TreeNode(7);
		TreeNode node8 = new TreeNode(8);
		TreeNode node9 = new TreeNode(9);
		TreeNode node10 = new TreeNode(10);
		TreeNode node11 = new TreeNode(11);
		root.left = node2;
		root.right = node3;
		node2.left = node4;
		node2.right = node5;
		node3.left = node6;
		node3.right = node7;
		node4.left = node8;
		node4.right = node9;
		node5.left = node10;
		node5.right = node11;
		node6.left =  null;
		node6.right = null;
		node7.left = null;
		node7.right = null;
		node8.left = null;
		node8.right = null;
		node9.left = null;
		node9.right = null;
		node10.left = null;
		node10.right = null;
		node11.left = null;
		node11.right = null;
		List<String> res = binaryTreePaths(root);
		System.out.println("All tree path:");
		for(int i = 0; i < res.size(); i++){
			System.out.println(res.get(i));
		}
		return;
	}	
}