请实现两个函数,分别用来序列化和反序列化二叉树。
剑指 Offer 37. 序列化二叉树 - 力扣(LeetCode) (leetcode-cn.com)
//序列化:利用队列先进先出的特点存储结点,
//如果取出的当前节点不是null,就把它的值添加到结果字符串,并把左右子节点(不管是否为null)加入队列;如果当前节点为null,就把“null”加入结果字符串
//反序列化:同样利用队列先进先出的特点存储已经构建好的节点
//先构建根节点加入队列,然后每次从队列取出一个节点,从字符串中取两个值,构建出当前节点的左右节点,将不为null的左右节点加入队列
public class Codec {
// Encodes a tree to a single string.
public String serialize(TreeNode root) {
if(root == null){
return null;
}
StringBuilder sb = new StringBuilder();
sb.append("[");
LinkedList<TreeNode> temp = new LinkedList();
TreeNode node = null;
temp.add(root);
while(temp.size() != 0){
node = temp.removeFirst();
if(node == null){
sb.append("null,");
}else{
sb.append(node.val);
sb.append(",");
temp.add(node.left);
temp.add(node.right);
}
}
sb.delete(sb.length() - 1, sb.length());
sb.append("]");
return sb.toString();
}
// Decodes your encoded data to tree.
public TreeNode deserialize(String data) {
if(data == null){
return null;
}
data = data.substring(1,data.length() - 1);
String[] s = data.split(",");
TreeNode root = new TreeNode(Integer.valueOf(s[0]));
LinkedList<TreeNode> list = new LinkedList<>();
list.add(root);
for(int i = 1; i < s.length; i += 2){
TreeNode node = list.removeFirst();
if(s[i].equals("null")){
node.left = null;
}else{
TreeNode left = new TreeNode(Integer.valueOf(s[i]));
node.left = left;
list.addLast(left);
}
if(s[i + 1].equals("null")){
node.right = null;
}else {
TreeNode right = new TreeNode(Integer.valueOf(s[i + 1]));
node.right = right;
list.addLast(right);
}
}
return root;
}
}