usaco-practice/usaco/Shell Game/index.cpp

using namespace std;

#include <cstdio>
#include <iostream>

int main() {
  freopen("shell.in", "r", stdin);
  freopen("shell.out", "w", stdout);

  int n;
  cin >> n;

  int score = 0;

  int a_values[n];
  int b_values[n];
  int g_values[n];
  for (int i = 0; i < n; i++) {
    cin >> a_values[i] >> b_values[i] >> g_values[i];
  }
  int shell_num;
  shell_num = 0;
  for (int i = 0; i < 3; i++) {
    shell_num = i + 1;
    for (int j = 0; j < n; j++) {
      int a, b, g;
      a = a_values[i];
      b = b_values[i];
      g = g_values[i];
      if (a == shell_num) {
        shell_num = b;
      } else if (b == shell_num) {
        shell_num = a;
      }
      if (g == shell_num) {
        score++;
      }
    }
  }
  cout << score << endl;
}