Base52 url shortener perfect hash function in C

  // decode a 5-digit base52 number
  unsigned long b52(const char *c) {
    unsigned long factor = 1;
    unsigned long result = 0;
    for(int i = 0; i < 5; i++) {
      result += factor * b52map[c[i]];
      factor *= 52;
    }
    return result;
  }

(52^5 < 2^32 so an 'unsigned long' is plenty; 52^11 < 2^64 so you could get an 11-digit base52 number into an 'unsigned long long'. I'd be tempted to generalize the function to handle 0-11 digits, by requiring the parameter to be null-terminated or passing in a length.)

trezor• 17 years ago

If your answer is a url shortener you are asking the wrong question.

lambdajones4• 17 years ago

I don't disagree. I tried to tell the product people that on several occasions, but it fell on deaf ears. So might as well do it right, eh?

Base52 url shortener perfect hash function in C

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