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djb2: This algorithm (k=33) was first reported by dan bernstein many years ago in comp.lang.c. another version of this algorithm (now favored by bernstein) uses xor: hash(i) = hash(i - 1) * 33 ^ str[i]; the magic of number 33 (why it works better than many other constants, prime or not) has never been adequately explained.
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/** | |
* hash_djb2 - implementation of the djb2 algorithm | |
* @str: string used to generate hash value | |
* | |
* Return: hash value | |
*/ | |
unsigned long int hash_djb2(const unsigned char *str) | |
{ | |
unsigned long int hash; | |
int c; | |
hash = 5381; | |
while ((c = *str++)) | |
{ | |
hash = ((hash << 5) + hash) + c; /* hash * 33 + c */ | |
} | |
return (hash); | |
} |
interesting to know about the djb2 algorithm.
It works as expected
the djb2 algorithm is sleek
Thank all good here
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Most interesting is the efficient use of bitwise left shift