LeetCode OJ:Serialize and Deserialize Binary Tree(对树序列化以及解序列化)
Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.
Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure.
For example, you may serialize the following tree
1 / \ 2 3 / \ 4 5
as "[1,2,3,null,null,4,5]"
, just the same as how LeetCode OJ serializes a binary tree. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.
这题实际上思路还是比较清晰的,遇见NULL的话那么存入一个#既可以了,解序列化的时候直接相应的处理#就可以了,代码如下:
1 /** 2 * Definition for a binary tree node. 3 * struct TreeNode { 4 * int val; 5 * TreeNode *left; 6 * TreeNode *right; 7 * TreeNode(int x) : val(x), left(NULL), right(NULL) {} 8 * }; 9 */ 10 class Codec { 11 public: 12 13 // Encodes a tree to a single string. 14 string serialize(TreeNode* root) { 15 queue<TreeNode *> q; 16 string str = ""; 17 if(!root) return str; 18 stringstream ss; 19 ss << root->val; 20 str += ss.str(); 21 q.push(root); 22 while(!q.empty()){ 23 TreeNode * t = q.front(); 24 if(t->left) q.push(t->left); 25 if(t->right) q.push(t->right); 26 if(t->left){ 27 ss.str(""); 28 ss << "," << t->left->val; 29 str += ss.str(); 30 }else{ 31 ss.str(""); 32 ss << "," << "#"; 33 str += ss.str(); 34 } 35 36 if(t->right){ 37 ss.str(""); 38 ss << "," << t->right->val; 39 str += ss.str(); 40 }else{ 41 ss.str(""); 42 ss << "," << "#"; 43 str += ss.str(); 44 } 45 q.pop(); 46 } 47 //删除末尾的#字符 48 for(int i = str.length() - 1; ; ){ 49 if(str[i] == '#'){ 50 str = str.substr(0, i - 1); 51 i = str.length() - 1; 52 }else{ 53 break; 54 } 55 } 56 return str; 57 } 58 59 // Decodes your encoded data to tree. 60 TreeNode* deserialize(string data) { 61 if(!data.size()) return NULL; 62 vector<string> dataVec; 63 int sz = data.length(); 64 for(int i = 0; i < sz;){//分割字符串,保存到vector中 65 if(data[i] != ','){ 66 int j = i; 67 for(; j < sz && data[j] != ','; ++j) 68 ; 69 string tmp = data.substr(i, j - i);//注意substr的使用细节 70 dataVec.push_back(tmp); 71 i = j + 1; //跳过','符号 72 } 73 } 74 sz = dataVec.size(); 75 TreeNode * root = new TreeNode(atoi(dataVec[0].c_str())); 76 queue<TreeNode *>q; 77 q.push(root); 78 int i = 1; 79 while(!q.empty() && i < sz){ 80 TreeNode * t = q.front(); 81 if(dataVec[i] != "#"){ 82 t->left = new TreeNode(atoi(dataVec[i].c_str())); 83 q.push(t->left); 84 }else{ 85 t->left = NULL; 86 } 87 i++; 88 if(i >= sz) break; 89 if(dataVec[i] != "#"){ 90 t->right = new TreeNode(atoi(dataVec[i].c_str())); 91 q.push(t->right); 92 }else{ 93 t->right = NULL; 94 } 95 q.pop(); 96 i++; 97 } 98 return root; 99 } 100 };
吐槽一下,c++连个split函数都没有,写起来真是恶心,还要自己去分割字符串。