## Serialize And Deserialize Binary Tree

07/17/2016 Tree Design

## Question

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.

Note: Do not use class member/global/static variables to store states. Your serialize and deserialize algorithms should be stateless.

## Solution

Result: Accepted Time: 16 ms

Here should be some explanations.

/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     struct TreeNode *left;
*     struct TreeNode *right;
* };
*/
/** Encodes a tree to a single string. */
char str[102400];
int ptr = 0;
void srlz(struct TreeNode * root)
{
if(root == NULL)
{
str[ptr++] = '#';
return ;
}
sprintf(str+ptr,"%d,",root->val);
while(str[ptr]) ptr++;
srlz(root->left);
srlz(root->right);
}

char* serialize(struct TreeNode* root) {
ptr = 0;
srlz(root);
str[ptr] = '\0';
return str;
}

struct TreeNode * dsrlz(char * data)
{
if(data[ptr] =='\0') return NULL;
if(data[ptr] == ',') ptr++;
if(data[ptr] == '#')
{
ptr++;
return NULL;
}
int tmp = 0;
int opt = 1;
if(data[ptr] == '-') opt = -1,ptr++;
while(isdigit(data[ptr])) tmp = tmp * 10 + opt*(data[ptr++] - '0');
struct TreeNode * root = malloc(sizeof(struct TreeNode));
root->val = tmp;
root->left = dsrlz(data);
root->right = dsrlz(data);
return root;
}

/** Decodes your encoded data to tree. */
struct TreeNode* deserialize(char* data) {
ptr = 0;
return dsrlz(data);
}

// Your functions will be called as such:
// char* data = serialize(root);
// deserialize(data);


Complexity Analytics

• Time Complexity: $O(n)$
• Space Complexity: $O(1)$