Encode and Decode TinyURL

Problem Summary

(Write in your own words, not copied from LeetCode. This forces comprehension.)

• Write encode() and decode() functions to convert a long url to a tiny url and vice versa
• https://leetcode.com/problems/encode-and-decode-tinyurl/ -> any tiny url
• any tiny url -> https://leetcode.com/problems/encode-and-decode-tinyurl/

Approach Taken

(Step-by-step logic or pseudocode before coding.)

• Instead of trying to come up with some crazy algorithm to convert a string into a smaller string we can simply use a counter
• Store counter to longUrl
• Map counter back to longUrl

Main Concepts Used

(Mark the CS concepts or algorithms used.)

• Hash Map
• Strings

Time & Space Complexity

• Time: $O(1)$ → Reason: Conversion is $O(1)$
• Space: $O(n)$ → Reason: Storing each long url in our map

Code

class Codec:
    def __init__(self):
        self.urlMap = {}
        self.base = 'https://tinyurl.com'

    def hash(self, input: str) -> str:
        return len(self.urlMap)

    def encode(self, longUrl: str) -> str:
        """Encodes a URL to a shortened URL."""
        key = self.hash(longUrl)
        tinyUrl = f'{self.base}/{key}'
        self.urlMap[tinyUrl] = longUrl
        return tinyUrl

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

Common Mistakes / Things I Got Stuck On

• Trying to come up with some crazy algorithm to convert a long string to a shorter string