So, now whenever the user visits the short URL, he will be redirected to the original URL. Url Shortener is a service that creates a short alias URL for a corresponding long URL. Val = "".The goal of the project is to design a Url shortener service like bit.ly or that is realtime scalable. Number = int(hex_str, 16) # first_n_chars(str(hex)) -> decimal This could be made much more efficient (even, for example by bisecting), but may be clearer as-is and depends hugely on unspecified algorithm requirements import hashlibīASE62 = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"ĭigest = m.digest() # hash as bytes b',\xdb3\x8c\x98g\xd6\x8b\x99\xb6\x98#.\\\xd1\x07\xa0\x8f\x1e\xb4\xab\x1eg\xdd\xda\xd6\xa3\x1d\xb0\xb2`9' This works by first hashing the value with an avalanching hash ( SHA-265) and then loops to find the minimum amount of it (slice from the front of the hex string) to form an 8-char base62 string Here's an example in Python which finds an 8-character string from the hash which should be fairly unique (this could then be collected into a sorted data structure mapping it into a URL) Here's a great video on cuckoo hashing (which is a structure of hashes relevant here): increment the size of the returned string.hash the result again (with your input).ignore them - they will be rare (ideally).However, there are many solutions for what to do for collisions Given that you are not hashing every url, but a vaguely-predictable number, you could hash the result and take the first N bits (I think there are more efficient algorithms for this, but the effect is the same and this is easiest to understand.) They repeat this until they pick an ID that hasn't been handed out. If they have, they pick a different random number. Then they check their DB to see if they've handed out that ID.If the URL identifiers are all supposed to be 8 ASCII characters, that means they pick a random number between 0 and 2^(8*8) = 1.844674407e19. When someone submits a URL, the system picks a random number between 0 and the highest-possible ID.But if they know how long they want the identifiers to be, it's not hard hand those IDs out in random order: For a variety of reasons, they don't want to hand those IDs out in order. So, the very first URL that gets submitted will be given ID=1: they save the whole URL in the database and associate it with that number. I think most URL shorteners work essentially by assigning a counting number to each URL that someone shortens. And that's without any kind of special, ZIP-like compression. 16 bits is just two ASCII characters, and three ASCII characters can accommodate nearly 17 million unique values. It takes 17 bits in binary: 11101010011000001 (not sure which endianness that is). Second: FMJQmhBR is not the most efficient way to represent the number 120001. If you've decided that each label will be a single letter from the English alphabet, then you only have enough unique labels for 26 guests. Let's say you've got 80 guests at a party, and you want to give each guest a unique label (for their drink cup or something). If your chosen representation has a maximum length, that imposes a hard limit on your key space. First: there absolutely is a compression limit.
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