# LeetCode 535. Encode and Decode TinyURL

## Description

https://leetcode.com/problems/encode-and-decode-tinyurl/

Note: This is a companion problem to the System Design problem: Design TinyURL.

TinyURL is a URL shortening service where you enter a URL such as `https://leetcode.com/problems/design-tinyurl` and it returns a short URL such as `http://tinyurl.com/4e9iAk`. Design a class to encode a URL and decode a tiny URL.

There is no restriction on how your encode/decode algorithm should work. You just need to ensure that a URL can be encoded to a tiny URL and the tiny URL can be decoded to the original URL.

Implement the `Solution` class:

• `Solution()` Initializes the object of the system.
• `String encode(String longUrl)` Returns a tiny URL for the given `longUrl`.
• `String decode(String shortUrl)` Returns the original long URL for the given `shortUrl`. It is guaranteed that the given `shortUrl` was encoded by the same object.

Example 1:

```Input: url = "https://leetcode.com/problems/design-tinyurl"
Output: "https://leetcode.com/problems/design-tinyurl"

Explanation:
Solution obj = new Solution();
string tiny = obj.encode(url); // returns the encoded tiny url.
string ans = obj.decode(tiny); // returns the original url after deconding it.
```

Constraints:

• `1 <= url.length <= 104`
• `url` is guranteed to be a valid URL.

## Explanation

For encoding, we can convert the long URL to hash code value and store it into a map. For decoding, we just need to use the hash code value from the short URL to get the original long URL.

## Python Solution

``````class Codec:
def __init__(self):
self.map = {}

def encode(self, longUrl: str) -> str:
"""Encodes a URL to a shortened URL.
"""

self.map[str(hash(longUrl))] = longUrl

return "http://tinyurl.com/" + str(hash(longUrl));

def decode(self, shortUrl: str) -> str:
"""Decodes a shortened URL to its original URL.
"""

shortUrl_hash = shortUrl.split("http://tinyurl.com/")[1]

return self.map[shortUrl_hash]

# Your Codec object will be instantiated and called as such:
# codec = Codec()
# codec.decode(codec.encode(url))
``````
• Time Complexity: O(N).
• Space Complexity: O(N).