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February 21, 2020 11:54
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hashing string to unique integer + padding (it can be compare)
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#define MAX_LENGTH 13 | |
unsigned long long MAX_LENGTH_VALUE; // 꽤 큰 값은 리터럴 상수 선언이 안되는 것 같다. | |
unsigned long long str2llu(const char s[MAX_LENGTH + 1]) { | |
unsigned long long r = 0, x = MAX_LENGTH_VALUE; | |
for (int i = 0; s[i]; ++i) { | |
r += x * (s[i] - 'a' + 1LLU); | |
x /= 27; | |
} | |
return r; | |
} | |
int main(){ | |
// 27 ^ (MAX_LENGTH - 1) 으로 만든다. | |
// 참고로 27^12 = 150,094,635,296,999,121 이다. | |
MAX_LENGTH_VALUE = 1; | |
for (int i = 0; i < MAX_LENGTH - 1; ++i) MAX_LENGTH_VALUE *= 27LLU; | |
assert(str2llu("aaa") < str2llu("ab")); // it should be true | |
return 0; | |
} |
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