113. Path Sum II

/**
 * 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 
{
    List<List<Integer>> l = new ArrayList<List<Integer>>();
    public void path(TreeNode root, int targetSum, List<Integer> l1)
    {
        if(root==null && targetSum==0)
        {
            List<Integer> l2 = new ArrayList<Integer>();
            for(int i=0;i<l1.size();i++)
                l2.add(l1.get(i));
            l.add(l2);
            return;
        }
        else if(root==null)
        {
            return;
        }
        targetSum-=root.val;
        l1.add(root.val);
        if(root.left==null)
            path(root.right,targetSum,l1);
        else if(root.right==null)
            path(root.left,targetSum,l1);
        else
        {
            path(root.right,targetSum,l1);
            path(root.left,targetSum,l1);
        }
        l1.remove(l1.size()-1);
        return;
            
    }
    public List<List<Integer>> pathSum(TreeNode root, int targetSum) 
    {
        l.clear();
        if(root==null)
            return l;
        List<Integer> l1 = new ArrayList<Integer>();
        path(root,targetSum,l1);
        return l;
    }
}