8. The path from the root node of the binary tree to the leaf node and the specified value

 

 

Title description

Given a binary tree and a value \sum sum, please find the path where the sum of the node values ​​from the root node to the leaf node is equal to \sum sum,
for example:
Given the following binary tree, \sum=22 sum=22,

Returns
[
[5,4,11,2],
[5,8,9]
]

Example 1

enter

{1,2},1

return value

[]

Example 2

enter

{1,2},3

return value

[[1,2]]

Code implementation :

import java.util.*;

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

public class Solution {
    /**
     * 
     * @param root TreeNode类 
     * @param sum int整型 
     * @return int整型ArrayList<ArrayList<>>
     */
private ArrayList<ArrayList<Integer>> listAll = new ArrayList<>();
private ArrayList<Integer> list = new ArrayList<>();
public ArrayList<ArrayList<Integer>> pathSum(TreeNode root, int target) {
	if (root == null) {
		return listAll;
	}
	list.add(root.val);
	target -= root.val;
	if (target == 0 && root.left == null && root.right == null) {
		listAll.add(new ArrayList<>(list));
	}
	pathSum(root.left, target);
	pathSum(root.right, target);
	// 回退
	list.remove(list.size() - 1);
	return listAll;
}
}