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myCircleHash
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// tested on gcc version 7.2.0 (Homebrew GCC 7.2.0 --with-jit) on macOS 10.12.6 | |
#include <string> | |
#include <iostream> | |
#include <functional> // std::hash | |
int NextCoprime(int (&c)[0xff], char x) | |
{ | |
return c[x] = (c[x] - x) * c[x] + x; | |
} | |
int NextPair(int a, int b, int (&c)[0xff], char x, char y) | |
{ | |
return a * NextCoprime(c, x) * std::hash<char>{}(x) + | |
b * std::hash<char>{}(y); | |
} | |
static int Hash(std::string s) | |
{ | |
int H = 0; | |
if (s.length() > 0) | |
{ | |
int a = s.length(), b = s.length() + 1; | |
int c[0xff] = {}; | |
for (int i = 0; i < 0xff; i++) | |
{ | |
c[i] = i + 1; | |
} | |
H = NextPair(a,b,c, s[s.length() - 1], s[0]); | |
for (unsigned i = 1; i < s.length(); i++) | |
{ | |
H ^= NextPair(a,b,c, s[i-1], s[i]); | |
} | |
} | |
return H; | |
} | |
int main() | |
{ | |
std::cout << Hash ("abcdef") << std::endl; | |
std::cout << Hash ("bcdefa") << std::endl; | |
std::cout << Hash ("cdefab") << std::endl; | |
std::cout << Hash ("cdfeab") << std::endl; | |
std::cout << Hash ("a0a0") << std::endl; | |
std::cout << Hash ("1010") << std::endl; | |
std::cout << Hash ("0abc0def0ghi") << std::endl; | |
std::cout << Hash ("0def0abc0ghi") << std::endl; | |
std::cout << Hash ("0def0ghi0abc") << std::endl; | |
// these three lines all returned 256293745 for me | |
} |
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