Binary Tree Paths

题目描述：

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"]

比较简单，直接上代码了，一次AC：

public class Solution {
    List<String> result=new ArrayList<String>();
	
	public List<String> binaryTreePaths(TreeNode root) {
		if(root==null)
			return result;
		String str="";
		getbinaryTreePaths(root, str);
		return result;
    }
	
	public void getbinaryTreePaths(TreeNode root,String str){
		if(root.left==null&&root.right==null){
			str+=root.val;
			result.add(str);
		}
		str+=root.val+"->";
		if(root.left!=null)
			getbinaryTreePaths(root.left, str);
		if(root.right!=null)
			getbinaryTreePaths(root.right, str);
	}
}