Submission #628156

#	Time	Username	Problem	Language	Result	Execution time	Memory
628156		Turkhuu	Thousands Islands (IOI22_islands)	C++17	Compilation error	0 ms	0 KiB

islands

#include <bits/stdc++.h>
using namespace std;
variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) {
  vector<vector<pair<int, int>>> G(N);
  for (int i = 0; i < M; i++) {
    G[U[i]].emplace_back(V[i], i);
  }
  vector<int> E(N, -1), ans, R(N);
  function<bool(int)> dfs = [&](int A) {
    R[A] = 1;
    for (auto [B, C] : G[A]) {
      if (E[A] != (C ^ 1)) {
        if (R[B] == 1) {
          vector<int> a;
          int F = B;
          while (F != 0) {
            a.push_back(E[F]);
            F = U[E[F]];
          }
          vector<int> c;
          int D = A;
          while (D != B) {
            c.push_back(E[D]);
            D = U[E[D]];
          }
          reverse(c.begin(), c.end());
          c.push_back(C);
          int s = c.size();
          for (int i = a.size() - 1; i >= 0; i--) {
            ans.push_back(a[i]);
          }
          for (int i = 0; i < s; i++) {
            for (int j = 0; j < s; j++) {
              ans.push_back(c[(s - i + j) % s]);
            }
            for (int j = 0; j < s; j++) {
              ans.push_back(c[(s - i + j) % s] ^ 1);
            }
          }
          for (int i = 0; i < a.size(); i++) {
            ans.push_back(a[i]);
          }
          return true;
        }
        if (R[B] == 0) {
          E[B] = C;
          if (dfs(B)) {
            return true;
          }
        }
      }
    }
    R[A] = 2;
    return false;
  };
  E[0] = -2;
  if (dfs(0)) {
    return ans;
  } else {
    return false;
  }
}
int main() {
  int N, M;
  assert(2 == scanf("%d %d", &N, &M));

  std::vector<int> U(M), V(M);
  for (int i = 0; i < M; ++i) {
    assert(2 == scanf("%d %d", &U[i], &V[i]));
  }

  std::variant<bool, std::vector<int>> result = find_journey(N, M, U, V);
  if (result.index() == 0) {
    printf("0\n");
    if (std::get<bool>(result)) {
      printf("1\n");
    } else {
      printf("0\n");
    }
  } else {
    printf("1\n");
    std::vector<int> &canoes = std::get<std::vector<int>>(result);
    printf("%d\n", static_cast<int>(canoes.size()));
    for (int i = 0; i < static_cast<int>(canoes.size()); ++i) {
      if (i > 0) {
        printf(" ");
      }
      printf("%d", canoes[i]);
    }
    printf("\n");
  }
  return 0;
}

Compilation message (stderr)

islands.cpp: In lambda function:
islands.cpp:40:29: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   40 |           for (int i = 0; i < a.size(); i++) {
      |                           ~~^~~~~~~~~~
/usr/bin/ld: /tmp/ccc33FKW.o: in function `main':
grader.cpp:(.text.startup+0x0): multiple definition of `main'; /tmp/ccq3jUwY.o:islands.cpp:(.text.startup+0x0): first defined here
collect2: error: ld returned 1 exit status