我一直在研究 C++ 中的 Rabin-Karp 字符串匹配函数,但没有得到任何结果。我有一种感觉,我没有正确计算某些值,但我不知道是哪一个。
原型
void rabinKarp(string sequence, string pattern, int d, int q);
功能实现
void rabinKarp(string sequence, string pattern, int d, int q)
{
//d is the |∑|
//q is the prime number to use to lessen spurious hits
int n = sequence.length(); //Length of the sequence
int m = pattern.length(); //Length of the pattern
double temp = static_cast<double> (m - 1.0);
double temp2 = pow(static_cast<double> (d), temp); //Exponentiate d
int h = (static_cast<int>(temp2)) % q; //High Order Position of an m-digit window
int p = 0; //Pattern decimal value
int t = 0; //Substring decimal value
for (int i = 1; i < m; i++) { //Preprocessing
p = (d*p + (static_cast<int>(pattern[i]) - 48)) % q;
t = (d*t + (static_cast<int>(sequence[i])-48)) % q;
}
for (int s = 0; s < (n-m); s++) { //Matching(Iterate through all possible shifts)
if (p == t) {
for (int j = 0; j < m; j++) {
if (pattern[j] == sequence[s+j]) {
cout << "Pattern occurs with shift: " << s << endl;
}
}
}
if (s < (n-m)) {
t = (d*(t - ((static_cast<int>(sequence[s+1]) - 48)*h)) + (static_cast<int>(sequence[s + m + 1]) - 48)) % q;
}
}
return;
}
在我的函数调用中,我传递 2359023141526739921 作为序列,31415 作为模式,10 作为基数,13 作为素数。我希望有一个实际匹配和一个虚假命中,但我从未从函数的匹配部分获得输出语句。我究竟做错了什么?
提前致谢,麦迪逊