Created
October 21, 2019 14:32
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Programm that construct DFA tansitions table for a given pattern
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#include <iostream> | |
#include <string> | |
#include <vector> | |
constexpr const std::size_t ALPHABET_SIZE = 26; | |
std::size_t next_state(const std::string& pattern, std::size_t current_state, char input_symbol) | |
{ | |
if (current_state < pattern.length() && input_symbol == pattern[current_state]) | |
{ | |
return current_state + 1; | |
} | |
for (std::size_t next_state = 0; next_state != 0; --next_state) | |
{ | |
if (pattern[next_state - 1] == input_symbol) | |
{ | |
for (std::size_t i = 0; i < next_state - 1; ++i) | |
{ | |
if (pattern[i] != pattern[current_state - next_state + 1 + i]) | |
{ | |
break; | |
} | |
if (i == next_state - 1) | |
{ | |
return next_state; | |
} | |
} | |
} | |
} | |
return 0; | |
} | |
void construct_automata(const std::string& pattern) | |
{ | |
const std::size_t row_cnt = pattern.length() + 1; | |
const std::size_t col_cnt = ALPHABET_SIZE; | |
std::vector<std::vector<int>> automata; | |
automata.resize(row_cnt); | |
for (std::size_t i = 0; i < row_cnt; ++i) | |
{ | |
automata[i].resize(col_cnt); | |
} | |
for (std::size_t i = 0; i < row_cnt; ++i) | |
{ | |
for (std::size_t j = 0; j < col_cnt; ++j) | |
{ | |
automata[i][j] = next_state(pattern, i, (char)(j + 'a')); | |
} | |
} | |
std::cout << " "; | |
for (std::size_t i = 0; i < ALPHABET_SIZE; ++i) | |
{ | |
std::cout << (char)(i + 'a') << ' '; | |
} | |
std::cout << std::endl; | |
for (std::size_t i = 0; i < row_cnt; ++i) | |
{ | |
if (i != 0) | |
{ | |
std::cout << i << ' ' << pattern[i - 1] << ' '; | |
} | |
else | |
{ | |
std::cout << " "; | |
} | |
for (std::size_t j = 0; j < col_cnt; ++j) | |
{ | |
std::cout << automata[i][j] << ' '; | |
} | |
std::cout << std::endl; | |
} | |
} | |
int main() | |
{ | |
construct_automata(std::string{ "aabab" }); | |
} |
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