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sub_string.hpp
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85 lines (70 loc) · 1.74 KB
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#include <string>
#include <vector>
#include <iostream>
namespace cppcode { namespace common {
enum class SUB_STRING_ALGORITHM : uint8_t
{
BRUTE_FORCE,
KMP
};
int32_t sub_string_brute_force(const std::string& s, const std::string& needle);
int32_t sub_string_KMP(const std::string& s, const std::string& needle);
int32_t sub_string(const std::string& s, const std::string& needle, const SUB_STRING_ALGORITHM sub_string_algorithm = SUB_STRING_ALGORITHM::BRUTE_FORCE)
{
switch (sub_string_algorithm)
{
case SUB_STRING_ALGORITHM::BRUTE_FORCE:
break;
case SUB_STRING_ALGORITHM::KMP:
return sub_string_KMP(s, needle);
default:
break;
}
return sub_string_brute_force(s, needle);
}
int32_t sub_string_brute_force(const std::string& s, const std::string& needle)
{
auto* p = s.data();
for (size_t i = 0; i < (s.size() - needle.size() + 1); i++)
{
if (std::string_view{p++, needle.size()} == needle)
{
return i;
}
}
return -1;
}
int32_t sub_string_KMP(const std::string& s, const std::string& needle)
{
std::vector<uint32_t> lps(needle.size(), 0);
int k = 0, i;
for (i = 1; i < needle.size(); i++)
{
while (k > 0 && needle[k] != needle[i])
{
k = lps[k - 1];
}
if (needle[k] == needle[i])
{
lps[i] = ++k;
}
}
k = 0;
for (i = 0; i < s.size(); i++)
{
while (k > 0 && s[i] != needle[k])
{
k = lps[k - 1];
}
if (s[i] == needle[k])
{
k++;
}
if (k == needle.size())
{
return i - needle.size() + 1;
}
}
return -1;
}
}}