leetcode给的二叉树形式
leetcode官方关于二叉树的解释
例如:
[5, 4, 7, 3, null, 2, null, -1, null, 9]
5
/ \
4 7
/ /
3 2
/ /
-1 9
在做二叉树的题目,有时出问题需要自己调试,这时候就要自己建树
- bfs
public class BinaryTreeCodes {
// Encodes a tree to a single string.
public String serialize(TreeNode root) {
if(root == null){
return "";
}
StringBuilder res = new StringBuilder();
res.append("[");
Queue<TreeNode> queue = new LinkedList<>();
queue.offer(root);
while(!queue.isEmpty()){
TreeNode node = queue.poll();
if(node != null){
res.append(node.val);
queue.offer(node.left);
queue.offer(node.right);
}else{
res.append("null");
}
res.append(",");
}
res.append("]");
return res.toString();
}
// Decodes your encoded data to tree.
public TreeNode deserialize(String data) {
if(data.equals("")){
return null;
}
String[] dataList = data.substring(1, data.length() - 1).split(",");
TreeNode root = new TreeNode(Integer.parseInt(dataList[0]));
Queue<TreeNode> queue = new LinkedList<>();
queue.offer(root);
int i = 1;
while(!queue.isEmpty()){
TreeNode node = queue.poll();
if(!"null".equals(dataList[i])){
node.left = new TreeNode(Integer.parseInt(dataList[i]));
queue.offer(node.left);
}
i++;
if(!"null".equals(dataList[i])){
node.right = new TreeNode(Integer.parseInt(dataList[i]));
queue.offer(node.right);
}
i++;
}
return root;
}
}