题解 | #二叉树中和为某一值的路径(二)#

二叉树前序遍历

import java.util.*;
import java.util.ArrayList;
/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;
    public TreeNode(int val) {
        this.val = val;
    }
}
*/
public class Solution {
    private ArrayList> res = new ArrayList();
    private LinkedList path = new LinkedList();
    public ArrayList> FindPath(TreeNode root,int expectNumber) {
        if(root == null){
            return res;
        }
        preOrder(root,expectNumber);
        return res;
    }
    public void preOrder(TreeNode root,int remainder){
        if(root.left == null && root.right == null){
            if(root.val == remainder){
                path.add(root.val);
                res.add(new ArrayList(path));
                path.removeLast();
            }

            return;
        }
        path.add(root.val);
        if(root.left != null){
            preOrder(root.left,remainder-root.val);
        }
        if(root.right != null){
            preOrder(root.right,remainder-root.val);
        }
        path.removeLast();
    }
}