LeetCode——Binary Tree Paths

Description：

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 Solution {
    public List<String> paths;
    public List<Integer> path;
    public List<String> binaryTreePaths(TreeNode root) {
        paths = new ArrayList<String>();
        path = new ArrayList<Integer>();
        getAllPath(root);

        return paths;
    }

    public void getAllPath(TreeNode node) {

    //       1
    //     /   \
    //    2     3    ["1->2->5", "1->3"]
    //     \
    //

        if(node == null) {
            return ;
        }
        path.add(node.val);
        if(node.left==null && node.right==null) {
            StringBuilder onePath = new StringBuilder();
            for(int i=0; i<path.size(); i++) {
                if(i != 0) onePath.append("->");
                onePath.append(path.get(i));
            }
            paths.add(onePath.toString());
        }
        getAllPath(node.left);
        getAllPath(node.right);
        path.remove(path.size() - 1);

    }
}