formalang/tests/NFAToDFA/check_equivalence.cpp

#include <gtest/gtest.h>
#include <random>
#include "DFA/DFAGraph.hpp"
#include "NFA/NFATree.hpp"
#include "converters/NFAToDFA.hpp"

using namespace NFA;
using namespace DFA;
using namespace converters;

std::mt19937 rnd(1337);

std::string GenerateRandomString(std::vector<char> alphabet, size_t len) {
  std::string res(len, ' ');
  for (auto& i: res) {
    i = alphabet[rnd() % alphabet.size()];
  }
  return res;
}

TEST(check_equivalence_NFA_to_DFA, 1) {
  NFA::NFATree tree;

  const int N = 10;
  int a[N];
  for (int i = 0; i < N; ++i)
    a[i] = tree.AddNewVertex();

  tree.GetVertex(a[0])->AddEdge('a', a[1]);
  tree.GetVertex(a[1])->AddEdge('a', a[2]);
  tree.GetVertex(a[0])->AddEdge('a', a[3]);

  tree.GetVertex(a[0])->SetStart(true);
  tree.GetVertex(a[2])->SetFinal(true);
  tree.GetVertex(a[3])->SetFinal(true);

  DFA::DFAGraph res = converters::NFATreeToDFAGraph(std::move(tree));

  EXPECT_FALSE(res.Accepted(""));
  EXPECT_TRUE(res.Accepted("a"));
  EXPECT_TRUE(res.Accepted("aa"));
  EXPECT_FALSE(res.Accepted("aaa"));
  EXPECT_FALSE(res.Accepted("aaaa"));
  EXPECT_FALSE(res.Accepted("aaaaa"));
  EXPECT_FALSE(res.Accepted("b"));
}

TEST(check_equivalence_NFA_to_DFA, 2) {
  NFA::NFATree tree;

  const int N = 10;
  int a[N];
  for (int i = 0; i < N; ++i)
    a[i] = tree.AddNewVertex();

  tree.GetVertex(a[0])->AddEdge('a', a[1]);
  tree.GetVertex(a[0])->AddEdge('a', a[2]);
  tree.GetVertex(a[1])->AddEdge('b', a[1]);
  tree.GetVertex(a[2])->AddEdge('c', a[2]);

  tree.GetVertex(a[0])->SetStart(true);
  tree.GetVertex(a[1])->SetFinal(true);
  tree.GetVertex(a[2])->SetFinal(true);

  DFA::DFAGraph res = converters::NFATreeToDFAGraph(std::move(tree));

  auto check = [](const std::string& str) {
    if (str.size() > 0) {
      if (str[0] == 'a') {
        if (str.size() == 1) {
          return true;
        }
        if (str[1] == 'b') {
          for (int i = 1; i < str.size(); ++i) {
            if (str[i] != 'b') {
              return false;
            }
          }
          return true;
        }
        if (str[1] == 'c') {
          for (int i = 1; i < str.size(); ++i) {
            if (str[i] != 'c') {
              return false;
            }
          }
          return true;
        }
      }
    }

    return false;
  };

  EXPECT_FALSE(res.Accepted(""));
  EXPECT_TRUE(res.Accepted("a"));
  EXPECT_FALSE(res.Accepted("aa"));
  EXPECT_FALSE(res.Accepted("aaa"));
  EXPECT_FALSE(res.Accepted("aaaa"));
  EXPECT_FALSE(res.Accepted("aaaaa"));
  EXPECT_FALSE(res.Accepted("b"));
  EXPECT_TRUE(res.Accepted("ab"));
  EXPECT_TRUE(res.Accepted("abb"));
  EXPECT_TRUE(res.Accepted("ac"));
  EXPECT_TRUE(res.Accepted("acc"));

  for (int i = 0; i < 5000; ++i) {
    auto str = GenerateRandomString({'a', 'b', 'c', 'd'}, 20);
    ASSERT_EQ(res.Accepted(str), check(str));
  }
}