Submission #826049

#	Time	Username	Problem	Language	Result	Execution time	Memory
826049		becaido	Thousands Islands (IOI22_islands)	C++17	24 / 100	47 ms	11040 KiB

islands

#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx,popcnt,sse4,abm")
#include <bits/stdc++.h>
using namespace std;
 
#ifndef WAIMAI
#include "islands.h"
#endif
 
#ifdef WAIMAI
#define debug(HEHE...) cout << "[" << #HEHE << "] : ", dout(HEHE)
void dout() {cout << '\n';}
template<typename T, typename...U>
void dout(T t, U...u) {cout << t << (sizeof...(u) ? ", " : ""), dout(u...);}
#else
#define debug(...) 7122
#endif
 
#define ll long long
#define Waimai ios::sync_with_stdio(false), cin.tie(0)
#define FOR(x,a,b) for (int x = a, I = b; x <= I; x++)
#define pb emplace_back
#define F first
#define S second
 
const int SIZE = 2e5 + 5;
 
int n, m;
int vs[SIZE];
vector<int> ans;
vector<pair<int, int>> adj[SIZE];
 
variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) {
    n = N, m = M;
    for (int i = 0; i < m; i += 2) adj[U[i]].pb(V[i], i);
    vector<pair<int, int>> all;
    auto dfs = [&](auto dfs, int pos)->bool {
        vs[pos] = 1;
        for (auto [np, id] : adj[pos]) {
            all.pb(pos, id);
            if (!vs[np]) {
                if (dfs(dfs, np)) return 1;
                all.pop_back();
                continue;
            }
            if (vs[np] == 2) {
                all.pop_back();
                continue;
            }
            int l, r = all.size() - 1;
            FOR (j, 0, r) if (all[j].F == np) {
                l = j;
                break;
            }
            FOR (j, 0, l - 1) ans.pb(all[j].S);
            FOR (j, l, r) ans.pb(all[j].S);
            FOR (j, l, r) ans.pb(all[j].S ^ 1);
            for (int j = r; j >= l; j--) ans.pb(all[j].S);
            for (int j = r; j >= l; j--) ans.pb(all[j].S ^ 1);
            for (int j = l - 1; j >= 0; j--) ans.pb(all[j].S);
            return 1;
        }
        vs[pos] = 2;
        return 0;
    };
    if (dfs(dfs, 0) == 0) return false;
    return ans;
}
 
/*
in1
4 5
0 1
1 2
2 3
0 3
3 1
out1
1
10
0 1 2 4 0 3 2 1 4 3
 
in2
2 3
0 1
1 0
1 0
out2
0
0
*/
 
#ifdef WAIMAI
int main() {
  int N, M;
  assert(2 == scanf("%d %d", &N, &M));
 
  vector<int> U(M), V(M);
  for (int i = 0; i < M; ++i) {
    assert(2 == scanf("%d %d", &U[i], &V[i]));
  }
 
  variant<bool, vector<int>> result = find_journey(N, M, U, V);
  if (result.index() == 0) {
    printf("0\n");
    if (get<bool>(result)) {
      printf("1\n");
    } else {
      printf("0\n");
    }
  } else {
    printf("1\n");
    vector<int> &canoes = get<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;
}
#endif

Compilation message (stderr)

islands.cpp: In lambda function:
islands.cpp:60:35: warning: 'l' may be used uninitialized in this function [-Wmaybe-uninitialized]
   60 |             for (int j = l - 1; j >= 0; j--) ans.pb(all[j].S);
      |                                 ~~^~~~
islands.cpp:59:31: warning: 'l' may be used uninitialized in this function [-Wmaybe-uninitialized]
   59 |             for (int j = r; j >= l; j--) ans.pb(all[j].S ^ 1);
      |                             ~~^~~~
islands.cpp: In function 'std::variant<bool, std::vector<int, std::allocator<int> > > find_journey(int, int, std::vector<int>, std::vector<int>)':
islands.cpp:59:31: warning: 'l' may be used uninitialized in this function [-Wmaybe-uninitialized]
   59 |             for (int j = r; j >= l; j--) ans.pb(all[j].S ^ 1);
      |                             ~~^~~~
islands.cpp:60:22: warning: 'l' may be used uninitialized in this function [-Wmaybe-uninitialized]
   60 |             for (int j = l - 1; j >= 0; j--) ans.pb(all[j].S);
      |                      ^
islands.cpp:21:20: warning: 'l' may be used uninitialized in this function [-Wmaybe-uninitialized]
   21 | #define FOR(x,a,b) for (int x = a, I = b; x <= I; x++)
      |                    ^~~
islands.cpp:50:17: note: 'l' was declared here
   50 |             int l, r = all.size() - 1;
      |                 ^
islands.cpp:59:31: warning: 'l' may be used uninitialized in this function [-Wmaybe-uninitialized]
   59 |             for (int j = r; j >= l; j--) ans.pb(all[j].S ^ 1);
      |                             ~~^~~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 5
• Subtask 3: 0 / 21
• Subtask 4: 24 / 24
• Subtask 5: 0 / 45