connected_components.cpp

#include <cstdio>
#include <iostream>

using namespace std;

inline int char_to_index(char c) { return c - 'a'; }
inline char index_to_char(int index) { return 'a' + index; }

int main(void) {
  int vertices_number = 0, edges_number = 0, test_case_number = 5;
  char sets[26];
  char v1, v2;
  cin >> test_case_number;

  for (int i = 0; i < test_case_number; i++) {
    // Reset sets
    for (int j = 0; j < 26; j++) sets[j] = index_to_char(j);

    scanf("%d %d\n", &vertices_number, &edges_number);

    for (int j = 0; j < edges_number; j++) {
      scanf("%c %c\n", &v1, &v2);
      sets[char_to_index(v2)] = sets[char_to_index(v1)];
    }

    cout << "Case #" << i + 1 << ":" << endl;
    int connected_cout = 0;
    for (int j = 0; j < vertices_number; j++) {
      char j_to_char = index_to_char(j);

      if (sets[j] != j_to_char) continue;

      for (int k = 0; k < vertices_number; k++) {
        if (sets[k] == j_to_char) cout << index_to_char(k) << ",";
      }

      if (sets[j] == j_to_char) {
        connected_cout++;
        cout << endl;
      }
    }
    cout << connected_cout << " connected components" << endl << endl;
  }  // for each test_case_number
}