leetcode -- Path Sum II

 Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.

For example:
Given the below binary tree and sum = 22,

              5
             / 
            4   8
           /   / 
          11  13  4
         /      / 
        7    2  5   1

return

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

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ArrayList<ArrayList<Integer>> pathSum(TreeNode root, int sum) {
        // Start typing your Java solution below
        // DO NOT write main() function
        ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
        if(root == null){
            return result;            
        }
        ArrayList<Integer> seqs = new ArrayList<Integer>();
        int curSum = 0;
        
        generatePathSum(root, result, seqs, curSum, sum);
        return result;
    }
    
    public void generatePathSum(TreeNode root, ArrayList<ArrayList<Integer>> result,
        ArrayList<Integer> seqs, int curSum, int expectedSum){
            curSum += root.val;
            seqs.add(root.val);
            
            boolean isLeaf = root.left == null && root.right == null;
            if(curSum == expectedSum && isLeaf){
                ArrayList<Integer> tmp = new ArrayList<Integer>();
                tmp.addAll(seqs);
                result.add(tmp);
            }
            
            if(root.left != null){
                generatePathSum(root.left, result, seqs, curSum, expectedSum);
            }
            
            if(root.right != null){
                generatePathSum(root.right, result, seqs, curSum, expectedSum);
            }
            
            seqs.remove(seqs.size() - 1);
            
        }
}

 refactor code:

public ArrayList<ArrayList<Integer>> pathSum(TreeNode root, int sum) {
        // Start typing your Java solution below
        // DO NOT write main() function
        ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
        if(root == null){
            return result;            
        }
        ArrayList<Integer> seqs = new ArrayList<Integer>();
        int curSum = 0;
        
        generatePathSum(root, result, seqs, curSum, sum);
        return result;
    }
    
    public void generatePathSum(TreeNode root, ArrayList<ArrayList<Integer>> result,
        ArrayList<Integer> seqs, int curSum, int expectedSum){
            curSum += root.val;
            seqs.add(root.val);
            
            boolean isLeaf = root.left == null && root.right == null;
            if(curSum == expectedSum && isLeaf){
                ArrayList<Integer> tmp = new ArrayList<Integer>();
                tmp.addAll(seqs);
                result.add(tmp);
                seqs.remove(seqs.size() - 1);
                return;
            }
            
            if(root.left != null){
                generatePathSum(root.left, result, seqs, curSum, expectedSum);
            }
            
            if(root.right != null){
                generatePathSum(root.right, result, seqs, curSum, expectedSum);
            }
            
            seqs.remove(seqs.size() - 1);
            
        }