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// 297. Serialize and Deserialize Binary Tree
#include "leetcode.h"
/*
* serialisation 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 acorss a network connection link to be reconstructed later in the
* same or another computer environment. design an algorithm to serialise and
* deserialise a binary tree. there is no restriction on how your serialisation
* and deserialisation algorithm shouldd work. you just need to ensure that a
* binary tree can be serialised to a string and this string can be deserialised
* to the original tree structure.
*/
struct list {
char **data;
int pos;
int size;
};
int comma_cnt(char *s) {
int cnt = 0;
while (*s != '\0') {
cnt += *s == ',';
++s;
};
return cnt;
}
struct list *split(char *s, int size) {
struct list *l = (struct list *)malloc(sizeof(struct list));
char **res = (char **)malloc(size * sizeof(char *)), *q = s;
for (int i = 0; i < size; ++i) {
while (*q != ',' && *q != '\0')
++q;
if (*q == ',') {
*q = '\0';
++q;
}
res[i] = s;
s = q;
}
l->data = res;
l->pos = 0;
l->size = size;
return l;
}
char *pop(struct list *l) {
if (l->pos >= l->size)
return NULL;
return l->data[l->pos++];
}
char *cleanup(char *s) {
int i = 0, j = 0;
if (s[j] == '[')
++j;
while (s[j] != ']' && s[j] != '\0') {
if (!isspace(s[j]))
s[i++] = s[j];
++j;
}
s[i] = '\0';
return s;
}
/** Encodes a tree to a single string. */
char *serialize(struct TreeNode *root) {
if (!root)
return NULL;
struct TreeNode *queue[21001];
int head = 0, tail = 0;
bool has_nodes;
struct TreeNode *n;
char *s = (char *)malloc(10 * sizeof(char)), num_str[10];
int sl = 1, max_sl = 10;
s[0] = '[';
queue[tail++] = root;
while (head != tail) {
n = queue[head++];
if (n) {
sprintf(num_str, "%d", n->val);
if (sl + strlen(num_str) + 4 >= max_sl) {
max_sl *= 2;
s = (char *)realloc(s, max_sl);
}
strcpy(s + sl, num_str);
sl += strlen(num_str);
s[sl++] = ',';
queue[tail++] = n->left;
queue[tail++] = n->right;
} else {
if (sl + 7 > max_sl) {
max_sl *= 2;
s = (char *)realloc(s, max_sl);
}
strcpy(s + sl, "null,");
sl += 5;
}
has_nodes = false;
for (int i = head; i < tail; i++)
if (queue[i]) {
has_nodes = true;
break;
}
if (!has_nodes)
head = tail;
}
s[sl - 1] = ']';
s[sl] = '\0';
return s;
}
/** Decodes your encoded data to tree. */
struct TreeNode *deserialize(char *data) {
if (!data)
return NULL;
data = cleanup(data);
int num_nodes = comma_cnt(data) + 1, head = 0, tail = 0;
struct list *l = split(data, num_nodes);
struct TreeNode *queue[num_nodes], *root, *n, *m;
char *entry = pop(l);
if (!entry)
return NULL;
root = (struct TreeNode *)malloc(sizeof(struct TreeNode));
root->val = atoi(entry);
root->left = NULL;
root->right = NULL;
queue[tail++] = root;
while (head != tail) {
n = queue[head++];
entry = pop(l);
if (entry && strcmp(entry, "null")) {
m = (struct TreeNode *)malloc(sizeof(struct TreeNode));
m->val = atoi(entry);
m->left = NULL;
m->right = NULL;
n->left = m;
queue[tail++] = m;
}
entry = pop(l);
if (entry && strcmp(entry, "null")) {
m = (struct TreeNode *)malloc(sizeof(struct TreeNode));
m->val = atoi(entry);
m->left = NULL;
m->right = NULL;
n->right = m;
queue[tail++] = m;
}
}
return root;
}
// Your functions will be called as such:
// char* data = serialize(root);
// deserialize(data);
int main() {
struct TreeNode *root = treenode_create(1);
root->left = treenode_create(2);
root->right = treenode_create(3);
root->right->left = treenode_create(4);
root->right->right = treenode_create(5);
char *data = serialize(root);
struct TreeNode *ds = deserialize(data);
treenode_print(ds); // expect: 1 2 3 nll null 4 5
treenode_free(root);
treenode_free(ds);
free(data);
}
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