535. Encode and Decode TinyURL LeetCode Solution

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Problem Statement
Complexity Analysis
Encode and Decode TinyURL solution in C++
Encode and Decode TinyURL solution in Java
Encode and Decode TinyURL solution in Python
Additional Resources

535. Encode and Decode TinyURL LeetCode Solution image

Problem Statement of 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 decoding it.

Constraints:

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

Complexity Analysis

Time Complexity:
Space Complexity:

535. Encode and Decode TinyURL LeetCode Solution in C++

class Solution {
 public:
  string encode(string longUrl) {
    while (!urlToCode.contains(longUrl)) {
      string code;
      for (int i = 0; i < 6; ++i)
        code += alphabets[rand() % alphabets.size()];
      if (!codeToUrl.contains(code)) {
        codeToUrl[code] = longUrl;
        urlToCode[longUrl] = code;
        return "http://tinyurl.com/" + code;
      }
    }

    throw;
  }

  string decode(string shortUrl) {
    return codeToUrl[shortUrl.substr(19)];
  }

 private:
  const string alphabets =
      "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
  unordered_map<string, string> urlToCode;
  unordered_map<string, string> codeToUrl;
};
/* code provided by PROGIEZ */

535. Encode and Decode TinyURL LeetCode Solution in Java

public class Codec {
  public String encode(String longUrl) {
    while (!urlToCode.containsKey(longUrl)) {
      StringBuilder sb = new StringBuilder();
      for (int i = 0; i < 6; ++i) {
        final char nextChar = alphabets.charAt(rand.nextInt(alphabets.length()));
        sb.append(nextChar);
      }
      final String code = sb.toString();
      if (!codeToUrl.containsKey(code)) {
        codeToUrl.put(code, longUrl);
        urlToCode.put(longUrl, code);
        return "http://tinyurl.com/" + code;
      }
    }

    throw new IllegalArgumentException();
  }

  public String decode(String shortUrl) {
    return codeToUrl.get(shortUrl.substring(19));
  }

  private static final String alphabets =
      "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
  private Map<String, String> urlToCode = new HashMap<>();
  private Map<String, String> codeToUrl = new HashMap<>();
  private Random rand = new Random();
}
// code provided by PROGIEZ

535. Encode and Decode TinyURL LeetCode Solution in Python

class Codec:
  alphabets = string.ascii_letters + '0123456789'
  urlToCode = {}
  codeToUrl = {}

  def encode(self, longUrl: str) -> str:
    while longUrl not in self.urlToCode:
      code = ''.join(random.choice(self.alphabets) for _ in range(6))
      if code not in self.codeToUrl:
        self.codeToUrl[code] = longUrl
        self.urlToCode[longUrl] = code
    return 'http://tinyurl.com/' + self.urlToCode[longUrl]

  def decode(self, shortUrl: str) -> str:
    return self.codeToUrl[shortUrl[-6:]]
 # code by PROGIEZ