Path Sum leetcode java

タイトル:
Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum. For example:
Given the below binary tree and sum = 22 ,

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

return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.
 
問題:
ツリーの操作、再帰的な解法です.
 1     
public 
boolean hasPathSum(TreeNode root, 
int sum) {
 2         
if(root == 
null) 
 3             
return 
false;
 4         
 5         sum -= root.val;
 6         
if(root.left == 
null && root.right==
null)  
 7             
return sum == 0;
 8         
else 
 9             
return hasPathSum(root.left,sum) || hasPathSum(root.right,sum);
10     }
 
非再帰的解法(Reference:http://www.programcreek.com/2013/01/leetcode-path-sum/):
 
 1     
public 
boolean hasPathSum(TreeNode root, 
int sum) {
 2         
if(root == 
null) 
return 
false;
 3  
 4         LinkedList nodes = 
new LinkedList();
 5         LinkedList values = 
new LinkedList();
 6  
 7         nodes.add(root);
 8         values.add(root.val);
 9  
10         
while(!nodes.isEmpty()){
11             TreeNode curr = nodes.poll();
12             
int sumValue = values.poll();
13  
14             
if(curr.left == 
null && curr.right == 
null && sumValue==sum){
15                 
return 
true;
16             }
17  
18             
if(curr.left != 
null){
19                 nodes.add(curr.left);
20                 values.add(sumValue+curr.left.val);
21             }
22  
23             
if(curr.right != 
null){
24                 nodes.add(curr.right);
25                 values.add(sumValue+curr.right.val);
26             }
27         }
28  
29         
return 
false;
30     }