LeetCode(算法)- 297. 二叉树的序列化与反序列化
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解题思路:略
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AC 代码
- Java
/**
* Definition for a binary tree node.
* public class TreeNode
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) val = x;
*
*/
// Your Codec object will be instantiated and called as such:
// Codec ser = new Codec();
// Codec deser = new Codec();
// TreeNode ans = deser.deserialize(ser.serialize(root));
// 解决方案(1)
public class Codec
public String serialize(TreeNode root)
StringBuilder sb = new StringBuilder();
Queue<TreeNode> queue = new LinkedList<TreeNode>()offer(root);;
while (!queue.isEmpty())
TreeNode node = queue.poll();
if (node == null)
sb.append(Integer.MAX_VALUE).append("#");
continue;
sb.append(node.val).append("#");
queue.offer(node.left);
queue.offer(node.right);
return sb.toString();
public TreeNode deserialize(String data)
String[] arr = data.split("#");
int ptrPar = arr.length - 1, ptrSub = arr.length - 1;
Map<Integer, TreeNode> nodeMap = new HashMap<>();
Map<TreeNode, TreeNode> parLMap = new HashMap<>();
Map<TreeNode, TreeNode> parRMap = new HashMap<>();
boolean flag = true;
while (ptrPar >= 0)
// 定位父亲指针
while (arr[ptrPar].equals(String.valueOf(Integer.MAX_VALUE)))
ptrPar--;
// 生成父节点
TreeNode parNode = new TreeNode(Integer.valueOf(arr[ptrPar]));
nodeMap.put(ptrPar--, parNode);
// 生成儿子节点
TreeNode lNode, rNode;
if (nodeMap.containsKey(ptrSub))
rNode = nodeMap.get(ptrSub);
else
Integer arrValue = Integer.valueOf(arr[ptrSub]);
rNode = new TreeNode(arrValue);
if (!arrValue.equals(Integer.MAX_VALUE))
flag = false;
if (flag)
parRMap.put(rNode, parNode);
ptrSub--;
if (nodeMap.containsKey(ptrSub))
lNode = nodeMap.get(ptrSub);
else
Integer arrValue = Integer.valueOf(arr[ptrSub]);
lNode = new TreeNode(arrValue);
if (!arrValue.equals(Integer.MAX_VALUE))
flag = false;
if (flag)
parLMap.put(lNode, parNode);
ptrSub--;
// 组合节点
parNode.right = rNode;
parNode.left = lNode;
// 满二叉树转换完全二叉树(去除末尾的 NULL)
convertTree(parLMap, parRMap);
return nodeMap.get(0);
private void convertTree(Map<TreeNode, TreeNode> parLMap, Map<TreeNode, TreeNode> parRMap)
for (Map.Entry<TreeNode, TreeNode> item : parLMap.entrySet())
item.getValue().left = null;
for (Map.Entry<TreeNode, TreeNode> item : parRMap.entrySet())
item.getValue().right = null;
// 解决方案(2)
public class Codec
public String serialize(TreeNode root)
if(root == null) return "[]";
StringBuilder res = new StringBuilder("[");
Queue<TreeNode> queue = new LinkedList<>() add(root); ;
while(!queue.isEmpty())
TreeNode node = queue.poll();
if(node != null)
res.append(node.val + ",");
queue.add(node.left);
queue.add(node.right);
else res.append("null,");
res.deleteCharAt(res.length() - 1);
res.append("]");
return res.toString();
public TreeNode deserialize(String data)
if(data.equals("[]")) return null;
String[] vals = data.substring(1, data.length() - 1).split(",");
TreeNode root = new TreeNode(Integer.parseInt(vals[0]));
Queue<TreeNode> queue = new LinkedList<>() add(root); ;
int i = 1;
while(!queue.isEmpty())
TreeNode node = queue.poll();
if(!vals[i].equals("null"))
node.left = new TreeNode(Integer.parseInt(vals[i]));
queue.add(node.left);
i++;
if(!vals[i].equals("null"))
node.right = new TreeNode(Integer.parseInt(vals[i]));
queue.add(node.right);
i++;
return root;
- C++
/**
* Definition for a binary tree node.
* struct TreeNode
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL)
* ;
*/
// Your Codec object will be instantiated and called as such:
// Codec ser, deser;
// TreeNode* ans = deser.deserialize(ser.serialize(root));
class Codec
public:
// Encodes a tree to a single string.
string serialize(TreeNode* root)
if(root == nullptr) return "[]";
string res = "[";
queue<TreeNode*> que;
que.emplace(root);
while(!que.empty())
TreeNode* node = que.front();
que.pop();
if(node != nullptr)
res += (to_string(node->val) + ",");
que.emplace(node->left);
que.emplace(node->right);
else res += "null,";
res.pop_back();
res += "]";
return res;
// Decodes your encoded data to tree.
TreeNode* deserialize(string data)
if (data == "[]")
return nullptr;
vector<string> list = split(data.substr(1, data.length() - 2), ",");
TreeNode *root = new TreeNode(std::stoi(list[0]));
queue<TreeNode*> que;
que.emplace(root);
int i = 1;
while(!que.empty())
TreeNode *node = que.front();
que.pop();
if(list[i] != "null")
node->left = new TreeNode(std::stoi(list[i]));
que.emplace(node->left);
i++;
if(list[i] != "null")
node->right = new TreeNode(std::stoi(list[i]));
que.emplace(node->right);
i++;
return root;
private:
// Split a str by a delim
vector<string> split(string str, string delim)
vector<string> list;
int i = 0, j = 0, len = str.length();
while (i < len)
while (j < len && str[j] != ',')
j++;
list.push_back(str.substr(i, j - i));
i = ++j;
return list;
;
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