Path Sum II

PathSum2.java

package com.interviewbytes.trees;

import java.util.ArrayList;
import java.util.List;

public class PathSum2 {

    public List<List<Integer>> pathSum(TreeNode root, int sum) {

        List<List<Integer>> paths = new ArrayList<>();
        helper(root, sum, paths, new ArrayList<Integer>());
        return paths;
    }

    private void helper(TreeNode node, int sum, List<List<Integer>> paths, List<Integer> path) {
        if (node == null) return;

        path.add(node.val);
        if (node.left == null && node.right == null && node.val == sum) {
            paths.add(new ArrayList<>(path));
        }
        helper(node.left, sum - node.val, paths, path);
        helper(node.right, sum - node.val, paths, path);
        path.remove(path.size() - 1);
    }
}

TreeNode.java

package com.interviewbytes.trees;

public class TreeNode {

    int val;
    TreeNode left;
    TreeNode right;

    TreeNode(int x) {
        val = x;
    }
}