Merge pull request neetcode-gh#2198 from seinlin/535

Add 0535-encode-and-decode-tinyurl.c

c/0535-encode-and-decode-tinyurl.c

@@ -0,0 +1,55 @@
+// Represent an element in a hash table.
+typedef struct Hash {
+ char* key;
+ char* value;
+ UT_hash_handle hh;
+} Hash;
+
+Hash *root = NULL;
+
+char *UrlToKey(char *url) {
+ char *key = NULL;
+ unsigned int hash = 1853;
+ int i = 0;
+
+ while (i < strlen(url)) {
+ hash = ((hash << 5) + hash) + url[i];
+ i++;
+ }
+
+ key = (char*)calloc(32, 1);
+ snprintf(key, 32, "http://tinyurl.com/%X", hash);
+ return key;
+}
+
+/** Encodes a URL to a shortened URL. */
+char* encode(char* longUrl) {
+ Hash *entry = NULL;
+ char *key = NULL;
+ key = UrlToKey(longUrl);
+ HASH_FIND_STR(root, key, entry);
+ if (!entry) {
+ entry = malloc(sizeof(Hash));
+ entry->key = key;
+ entry->value = longUrl;
+ HASH_ADD_KEYPTR(hh, root, key, strlen(key), entry);
+ } else {
+ free(key);
+ }
+ return entry->key;
+}
+
+/** Decodes a shortened URL to its original URL. */
+char* decode(char* shortUrl) {
+ Hash *entry = NULL;
+ HASH_FIND_STR(root, shortUrl, entry);
+ if (entry) {
+ return entry->value;
+ }
+ return NULL;
+}
+
+// Your functions will be called as such:
+// char* s = encode(s);
+// decode(s);
+