pathSum.java

class Solution {
    public List<List<Integer>> pathSum(TreeNode root, int sum){
  List<List<Integer>> result  = new LinkedList<List<Integer>>();
  List<Integer> currentResult  = new LinkedList<Integer>();
  pathSum(root,sum,currentResult,result);
  return result;
}

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

  if (root == null)
    return;
  currentResult.add(new Integer(root.val));
  if (root.left == null && root.right == null && sum == root.val) {
    result.add(new LinkedList(currentResult));
    currentResult.remove(currentResult.size() - 1);
    return;
  } else {
    pathSum(root.left, sum - root.val, currentResult, result);
    pathSum(root.right, sum - root.val, currentResult, result);
  }
  currentResult.remove(currentResult.size() - 1);
}
}