1、什么是二叉树的序列化与反序列化
二叉树就是节点在内存区域中串联起来的，但是如果掉电，内存上的数据就没有了。为了保存这种结构，将二叉树用字符串的形式保存到硬盘中，这就是序列化；从字符串形式转换为二叉树，这就是反序列化。
唯一的字符串会对应唯一的结构，唯一的结构也会对应唯一的字符串，即字符串和二叉树是一一对应的。
【思路】首先认为 NULL 是不可忽略的，遇到 NULL 就用 # 或者其他字符代替。且每访问结束一个节点，用分隔符隔开。
2、先序方式序列化和反序列化
【例子】
上图红色数字就是先序遍历的顺序，所以得到的字符串就是 “1，1，#，1，#，#，#”。
之所以要用分隔符隔开，是为了防止二义性，比如如下两棵树：
【代码实现】
//先序序列化二叉树
void preS(TreeNode *root, queue<string> &ans) {
if (root == nullptr)
ans.push("#");
else {
//每个节点转成的字符串保存到队列中
ans.push(to_string(root->value));
preS(root->lchild, ans);
preS(root->rchild, ans);
}
}
queue<string> preOrderSerial(TreeNode *root) {
queue<string> ans;
preS(root, ans);
return ans;
}
TreeNode *preb(queue<string> &prelist) {
string value = prelist.front();
prelist.pop();
//空树
if (value == "#") return nullptr;
TreeNode *root = new TreeNode(stoi(value)); //每个节点字符串转成整数
root->lchild = preb(prelist);
root->rchild = preb(prelist);
return root;
}
//以先序序列化还原二叉树, 即反序列化
TreeNode *buildByPreQueue(queue<string> &prelist) {
if (prelist.size() == 0) return nullptr;
return preb(prelist);
}3、后序方式序列化和反序列化
//后序序列化
void posS(TreeNode *root, queue<string> &ans) {
if (root == nullptr)
ans.push("#");
else {
posS(root->lchild, ans);
posS(root->rchild, ans);
ans.push(to_string(root->value));
}
}
queue<string> posOrderSerial(TreeNode *root) {
queue<string> ans;
posS(root, ans);
return ans;
}
//后序反序列化
TreeNode *posB(stack<string> &posstack) {
string value = posstack.top();
posstack.pop();
if (value == "#") return nullptr;
TreeNode *root = new TreeNode(stoi(value));
root->rchild = posB(posstack);
root->lchild = posB(posstack);
return root;
}
TreeNode *buildByPosQueue(queue<string> &poslist) {
if (poslist.size() == 0)
return nullptr;
stack<string> sta; //栈中的顺序为：中右左
while (!poslist.empty()) {
sta.push(poslist.front());
poslist.pop();
}
return posB(sta);
}4、层序方式序列化和反序列化
//层序序列化
queue<string> levelSerial(TreeNode *root) {
queue<string> ans;
if (root == nullptr) {
ans.push("#");
} else {
ans.push(to_string(root->value));
//准备队列，用于层序遍历
queue<TreeNode *> que;
que.push(root);
while (!que.empty()) {
TreeNode *cur = que.front();
que.pop();
if (cur->lchild != nullptr) {
ans.push(to_string(cur->lchild->value));
que.push(cur->lchild);
} else {
ans.push("#");
}
if (cur->rchild != nullptr) {
ans.push(to_string(cur->rchild->value));
que.push(cur->rchild);
} else {
ans.push("#");
}
}
}
return ans;
}
//层序反序列化
TreeNode *generateTreeNode(string str) {
if (str == "#") return nullptr;
return new TreeNode(stoi(str));
}
TreeNode *buildByLevelQueue(queue<string> &levelList) {
if (levelList.size() == 0) {
return nullptr;
}
TreeNode *root = generateTreeNode(levelList.front());
levelList.pop();
queue<TreeNode *> que;
if (root != nullptr) {
que.push(root);
}
TreeNode *cur = nullptr;
while (!que.empty()) {
cur = que.front();
que.pop();
cur->lchild = generateTreeNode(levelList.front());
levelList.pop();
cur->rchild = generateTreeNode(levelList.front());
levelList.pop();
if (cur->lchild != nullptr) {
que.push(cur->lchild);
}
if (cur->rchild != nullptr) {
que.push(cur->rchild);
}
}
return root;
}5、完整代码 C++ 版
#include <iostream>
#include <cstring>
#include <queue>
#include <ctime>
#include <stack>
using namespace std;
class TreeNode {
public:
int value;
TreeNode *lchild;
TreeNode *rchild;
TreeNode(int data) : value(data) {}
};
//先序序列化二叉树
void preS(TreeNode *root, queue<string> &ans) {
if (root == nullptr)
ans.push("#");
else {
//每个节点转成的字符串保存到队列中
ans.push(to_string(root->value));
preS(root->lchild, ans);
preS(root->rchild, ans);
}
}
queue<string> preOrderSerial(TreeNode *root) {
queue<string> ans;
preS(root, ans);
return ans;
}
//以先序序列化还原二叉树, 即反序列化
TreeNode *preb(queue<string> &prelist) {
string value = prelist.front();
prelist.pop();
//空树
if (value == "#") return nullptr;
TreeNode *root = new TreeNode(stoi(value)); //每个节点字符串转成整数
root->lchild = preb(prelist);
root->rchild = preb(prelist);
return root;
}
TreeNode *buildByPreQueue(queue<string> &prelist) {
if (prelist.size() == 0) return nullptr;
return preb(prelist);
}
//后序序列化
void posS(TreeNode *root, queue<string> &ans) {
if (root == nullptr)
ans.push("#");
else {
posS(root->lchild, ans);
posS(root->rchild, ans);
ans.push(to_string(root->value));
}
}
queue<string> posOrderSerial(TreeNode *root) {
queue<string> ans;
posS(root, ans);
return ans;
}
//后序反序列化
TreeNode *posB(stack<string> &posstack) {
string value = posstack.top();
posstack.pop();
if (value == "#") return nullptr;
TreeNode *root = new TreeNode(stoi(value));
root->rchild = posB(posstack);
root->lchild = posB(posstack);
return root;
}
TreeNode *buildByPosQueue(queue<string> &poslist) {
if (poslist.size() == 0)
return nullptr;
stack<string> sta; //栈中的顺序为：中右左
while (!poslist.empty()) {
sta.push(poslist.front());
poslist.pop();
}
return posB(sta);
}
//层序序列化
queue<string> levelSerial(TreeNode *root) {
queue<string> ans;
if (root == nullptr) {
ans.push("#");
} else {
ans.push(to_string(root->value));
//准备队列，用于层序遍历
queue<TreeNode *> que;
que.push(root);
while (!que.empty()) {
TreeNode *cur = que.front();
que.pop();
if (cur->lchild != nullptr) {
ans.push(to_string(cur->lchild->value));
que.push(cur->lchild);
} else {
ans.push("#");
}
if (cur->rchild != nullptr) {
ans.push(to_string(cur->rchild->value));
que.push(cur->rchild);
} else {
ans.push("#");
}
}
}
return ans;
}
//层序反序列化
TreeNode *generateTreeNode(string str) {
if (str == "#") return nullptr;
return new TreeNode(stoi(str));
}
TreeNode *buildByLevelQueue(queue<string> &levelList) {
if (levelList.size() == 0) {
return nullptr;
}
TreeNode *root = generateTreeNode(levelList.front());
levelList.pop();
queue<TreeNode *> que;
if (root != nullptr) {
que.push(root);
}
TreeNode *cur = nullptr;
while (!que.empty()) {
cur = que.front();
que.pop();
cur->lchild = generateTreeNode(levelList.front());
levelList.pop();
cur->rchild = generateTreeNode(levelList.front());
levelList.pop();
if (cur->lchild != nullptr) {
que.push(cur->lchild);
}
if (cur->rchild != nullptr) {
que.push(cur->rchild);
}
}
return root;
}
//for test
TreeNode *generate(int level, int maxLevel, int maxValue) {
if (level > maxLevel || rand() % 100 < 0.5) return nullptr;
TreeNode *root = new TreeNode(rand() % maxValue);
root->lchild = generate(level + 1, maxLevel, maxValue);
root->rchild = generate(level + 1, maxLevel, maxValue);
return root;
}
TreeNode *generateRandomBST(int maxLen, int maxVal) {
return generate(1, maxLen, maxVal);
}
bool isSameValueStructure(TreeNode *root1, TreeNode *root2) {
if (root1 == nullptr && root2 != nullptr)
return false;
if (root1 != nullptr && root2 == nullptr)
return false;
if (root1 == nullptr && root2 == nullptr)
return true;
if (root1->value != root2->value)
return false;
return isSameValueStructure(root1->lchild, root2->lchild) && isSameValueStructure(root1->rchild, root2->rchild);
}
string getSpace(int num) {
string space = "";
for (int i = 0; i < num; i++) {
space += " ";
}
return space;
}
void printInOrder(TreeNode *root, int height, string to, int len) {
if (root == nullptr) return ;
printInOrder(root->rchild, height + 1, "v", len);
string val = to + to_string(root->value) + to;
int lenM = val.length();
int lenL = (len - lenM) / 2;
int lenR = len - lenM - lenL;
val = getSpace(lenL) + val + getSpace(lenR);
cout << getSpace(height * len) + val << endl;
printInOrder(root->lchild, height + 1, "^", len);
}
void printTree(TreeNode *root) {
cout << "Binary Tree:" << endl;
printInOrder(root, 0, "H", 7);
cout << endl;
}
int main() {
srand(time(0));
int maxLevel = 5;
int maxValue = 100;
int testTime = 1000000;
cout << "test begin" << endl;
for (int i = 0; i < testTime + 1; i++) {
TreeNode *root = generateRandomBST(maxLevel, maxValue);
queue<string> pre = preOrderSerial(root);
queue<string> post = posOrderSerial(root);
queue<string> level = levelSerial(root);
TreeNode *preBuild = buildByPreQueue(pre);
TreeNode *posBuild = buildByPosQueue(post);
TreeNode *levelBuild = buildByLevelQueue(level);
if (!isSameValueStructure(preBuild, posBuild) || !isSameValueStructure(posBuild, levelBuild)) {
cout << "Oops!" << endl;
break;
}
if (i && i % 100 == 0) cout << i << " cases passed!" << endl;
}
cout << "test finish!" << endl;
return 0;
}Java 版
package class11;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;
public class Code02_SerializeAndReconstructTree {
public static class Node {
public int value;
public Node left;
public Node right;
public Node(int data) {
this.value = data;
}
}
public static Queue<String> preSerial(Node head) {
Queue<String> ans = new LinkedList<>();
pres(head, ans);
return ans;
}
public static void pres(Node head, Queue<String> ans) {
if (head == null) {
ans.add(null);
} else {
ans.add(String.valueOf(head.value));
pres(head.left, ans);
pres(head.right, ans);
}
}
public static Queue<String> inSerial(Node head) {
Queue<String> ans = new LinkedList<>();
ins(head, ans);
return ans;
}
public static void ins(Node head, Queue<String> ans) {
if (head == null) {
ans.add(null);
} else {
ins(head.left, ans);
ans.add(String.valueOf(head.value));
ins(head.right, ans);
}
}
public static Queue<String> posSerial(Node head) {
Queue<String> ans = new LinkedList<>();
poss(head, ans);
return ans;
}
public static void poss(Node head, Queue<String> ans) {
if (head == null) {
ans.add(null);
} else {
poss(head.left, ans);
poss(head.right, ans);
ans.add(String.valueOf(head.value));
}
}
public static Node buildByPreQueue(Queue<String> prelist) {
if (prelist == null || prelist.size() == 0) {
return null;
}
return preb(prelist);
}
public static Node preb(Queue<String> prelist) {
String value = prelist.poll();
if (value == null) {
return null;
}
Node head = new Node(Integer.valueOf(value));
head.left = preb(prelist);
head.right = preb(prelist);
return head;
}
public static Node buildByPosQueue(Queue<String> poslist) {
if (poslist == null || poslist.size() == 0) {
return null;
}
// 左右中 -> stack(中右左)
Stack<String> stack = new Stack<>();
while (!poslist.isEmpty()) {
stack.push(poslist.poll());
}
return posb(stack);
}
public static Node posb(Stack<String> posstack) {
String value = posstack.pop();
if (value == null) {
return null;
}
Node head = new Node(Integer.valueOf(value));
head.right = posb(posstack);
head.left = posb(posstack);
return head;
}
public static Queue<String> levelSerial(Node head) {
Queue<String> ans = new LinkedList<>();
if (head == null) {
ans.add(null);
} else {
ans.add(String.valueOf(head.value));
Queue<Node> queue = new LinkedList<Node>();
queue.add(head);
while (!queue.isEmpty()) {
head = queue.poll(); // head 父 子
if (head.left != null) {
ans.add(String.valueOf(head.left.value));
queue.add(head.left);
} else {
ans.add(null);
}
if (head.right != null) {
ans.add(String.valueOf(head.right.value));
queue.add(head.right);
} else {
ans.add(null);
}
}
}
return ans;
}
public static Node buildByLevelQueue(Queue<String> levelList) {
if (levelList == null || levelList.size() == 0) {
return null;
}
Node head = generateNode(levelList.poll());
Queue<Node> queue = new LinkedList<Node>();
if (head != null) {
queue.add(head);
}
Node node = null;
while (!queue.isEmpty()) {
node = queue.poll();
node.left = generateNode(levelList.poll());
node.right = generateNode(levelList.poll());
if (node.left != null) {
queue.add(node.left);
}
if (node.right != null) {
queue.add(node.right);
}
}
return head;
}
public static Node generateNode(String val) {
if (val == null) {
return null;
}
return new Node(Integer.valueOf(val));
}
// for test
public static Node generateRandomBST(int maxLevel, int maxValue) {
return generate(1, maxLevel, maxValue);
}
// for test
public static Node generate(int level, int maxLevel, int maxValue) {
if (level > maxLevel || Math.random() < 0.5) {
return null;
}
Node head = new Node((int) (Math.random() * maxValue));
head.left = generate(level + 1, maxLevel, maxValue);
head.right = generate(level + 1, maxLevel, maxValue);
return head;
}
// for test
public static boolean isSameValueStructure(Node head1, Node head2) {
if (head1 == null && head2 != null) {
return false;
}
if (head1 != null && head2 == null) {
return false;
}
if (head1 == null && head2 == null) {
return true;
}
if (head1.value != head2.value) {
return false;
}
return isSameValueStructure(head1.left, head2.left) && isSameValueStructure(head1.right, head2.right);
}
// for test
public static void printTree(Node head) {
System.out.println("Binary Tree:");
printInOrder(head, 0, "H", 17);
System.out.println();
}
public static void printInOrder(Node head, int height, String to, int len) {
if (head == null) {
return;
}
printInOrder(head.right, height + 1, "v", len);
String val = to + head.value + to;
int lenM = val.length();
int lenL = (len - lenM) / 2;
int lenR = len - lenM - lenL;
val = getSpace(lenL) + val + getSpace(lenR);
System.out.println(getSpace(height * len) + val);
printInOrder(head.left, height + 1, "^", len);
}
public static String getSpace(int num) {
String space = " ";
StringBuffer buf = new StringBuffer("");
for (int i = 0; i < num; i++) {
buf.append(space);
}
return buf.toString();
}
public static void main(String[] args) {
int maxLevel = 5;
int maxValue = 100;
int testTimes = 1000000;
System.out.println("test begin");
for (int i = 0; i < testTimes; i++) {
Node head = generateRandomBST(maxLevel, maxValue);
Queue<String> pre = preSerial(head);
Queue<String> pos = posSerial(head);
Queue<String> level = levelSerial(head);
Node preBuild = buildByPreQueue(pre);
Node posBuild = buildByPosQueue(pos);
Node levelBuild = buildByLevelQueue(level);
if (!isSameValueStructure(preBuild, posBuild) || !isSameValueStructure(posBuild, levelBuild)) {
System.out.println("Oops!");
}
}
System.out.println("test finish!");
}
}到此这篇关于Java版本和C++版本的二叉树序列化与反序列化的文章就介绍到这了,更多相关Java与C++二叉树序列化 内容请搜索编程网以前的文章或继续浏览下面的相关文章希望大家以后多多支持编程网！
