Serialize and Deserialize Binary Tree
序列化和反序列化一个二叉树. 需要注意两个特殊情况, 一个是node是null的情况, 一个是 node直接的分隔号.
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Codec {
private static final String spliter = ",";
private static final String NN = "X";
// Encodes a tree to a single string.
public String serialize(TreeNode root) {
StringBuilder sb = new StringBuilder();
build(root, sb);
return sb.toString();
}
private void build(TreeNode root, StringBuilder sb) {
if(root == null)
sb.append(NN).append(spliter);
else{
sb.append(root.val).append(spliter);
build(root.left, sb);
build(root.right, sb);
}
}
// Decodes your encoded data to tree.
public TreeNode deserialize(String data) {
Deque<String> nodes = new LinkedList<>();
nodes.addAll(Arrays.asList(data.split(spliter)));
return buildTree(nodes);
}
private TreeNode buildTree(Deque<String> nodes) {
String val = nodes.remove();
if(val.equals(NN))
return null;
TreeNode node = new TreeNode(Integer.valueOf(val));
node.left = buildTree(nodes);
node.right = buildTree(nodes);
return node;
}
}
// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.deserialize(codec.serialize(root));