NC_8_BINARYTREE_SUMPATH

package org.example.interview.practice;

import java.util.ArrayList;

/**
 * @author xianzhe.ma
 * @date 2021/7/12
 * 求和为某个值的所哟路径
 */

public class NC_8_BINARYTREE_SUMPATH {

    public static ArrayList<ArrayList<Integer>> pathSum(TreeNode root, int sum) {
        // write code here
        ArrayList<Integer> list = new ArrayList<>();
        ArrayList<ArrayList<Integer>> lists = new ArrayList<>();
        dfs(lists, list, 0, sum, root);
        return lists;
    }

    private static void dfs(ArrayList<ArrayList<Integer>> lists, ArrayList<Integer> list,
                            int sum, int k, TreeNode root) {
        if (root == null) {
            return;
        }

        sum += root.val;
        list.add(root.val);
        if (root.left == null && root.right == null) {
            if (sum == k) {
                ArrayList<Integer> gg = new ArrayList<>();
                for (int l : list) {
                    gg.add(l);
                }
                //*注意list里面嵌入list的时候 改变里面的list会改变外层list 即添加进去的是引用*
                lists.add(gg);
            }
            list.remove(list.size() - 1);
            return;
        }
        dfs(lists, list, sum, k, root.left);
        dfs(lists, list, sum, k, root.right);
        list.remove(list.size() - 1);
    }

    public static class TreeNode {
        int val = 0;
        TreeNode left = null;
        TreeNode right = null;
    }

    public static void main(String[] args) {
        TreeNode node = new TreeNode();
        node.val = 1;

        TreeNode leftChild = new TreeNode();
        leftChild.val = 2;

        node.left = leftChild;

        ArrayList<ArrayList<Integer>> result = pathSum(node, 3);
        for (ArrayList<Integer> list : result) {
            System.out.println(list.toString());
        }
    }
}