solution_1.txt

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public List<List<Integer>> pathSum(TreeNode root, int targetSum) {
        List<List<Integer>> result = new ArrayList<>();
        Sum(root, targetSum, result, new ArrayList<Integer>());
        return result;
    }
    
    private void Sum(TreeNode node, int targetSum, List<List<Integer>> result, ArrayList<Integer> lists){
        if (node == null) return;
        if (node.left == null && node.right == null && targetSum == node.val) {
            lists.add(node.val);
            result.add(new ArrayList<Integer>(lists));
            lists.remove(lists.size() - 1);
            return;
        } 
        
        lists.add(node.val);
        
        Sum(node.left, targetSum - node.val, result, lists);
        Sum(node.right, targetSum - node.val, result, lists);
        
        lists.remove(lists.size() - 1);
    }
}