Prove safety offerNo24. Binary tree and a path value (Java)

Subject description:

An input binary tree root node and an integer, the binary print values ​​of nodes in the input path and all integers. Forming a path to the path definition begins from the root node of the tree down to the leaf node has been traversed nodes. (Note: the return value in the list, a large array Array front)

Example above: integer input 22, the path may be printed with a (10,5,7) and (10, 12)

Ideas:

The whole process using the depth-first traversal DFS.

Code:

package offer;

import org.omg.PortableInterceptor.INACTIVE;
import sun.reflect.generics.tree.Tree;

import java.util.ArrayList;
import java.util.Stack;

public class TestNo24 {
    static class TreeNode{
        int val;
        TreeNode left;
        TreeNode right;
        TreeNode(int val){
            this.val = val;
        }
    }
    public static void main(String[] args) {
        TreeNode root = new TreeNode(10);
        TreeNode node1 = new TreeNode(5);
        TreeNode node2 = new TreeNode(12);
        TreeNode node3 = new TreeNode(4);
        TreeNode node4 = new TreeNode(7);
        root.left = node1;
        root.right = node2;
        node1.left = node3;
        node1.right = node4;
        System.out.println(new TestNo24().FindPath(root,22));

    }
    ArrayList<ArrayList<Integer>> ret = new ArrayList<>();
    public ArrayList<ArrayList<Integer>> FindPath(TreeNode root,int target) {
        if(root == null ){
            return ret;
        }
        //递归调用
        findPath(root,target,new ArrayList<>());
        return ret;
    }
    public void findPath(TreeNode root, int target, ArrayList<Integer> cache){
        if(root == null){
            return;
        }
        int val = root.val;
        int remainVal = target-val;
        //当前节点列表
        cache.add(val);
        if(remainVal == 0 && root.left == null && root.right == null){
            ret.add(new ArrayList<>(cache));
        }
        //处理叶子节点

        findPath(root.left,remainVal,cache);
        findPath(root.right,remainVal,cache);
        //回溯到上一个节点
        cache.remove(cache.size()-1);
    }

}