Submission #634752

#	Time	Username	Problem	Language	Result	Execution time	Memory
634752		Cauchico	Thousands Islands (IOI22_islands)	C++17	0 / 100	1 ms	468 KiB

islands

#include <variant>
#include <bits/stdc++.h>
using namespace std;

vector<vector<pair<int,int>>> adj;
vector<vector<int>> adj_rev;
vector<int> path; 
vector<bool> used;
int loop = -1;

void dfs(int v) {
    used[v] = true;
    for (auto u: adj[v]) {
        if (!used[u.first]) {
            path.push_back(u.second);
            dfs(u.first);
        } else {
            path.push_back(u.second);
            loop = u.first;
            return;
        }
        if (loop == -1) {
            path.pop_back();
        } else {
            return;
        }
    }
}

vector<bool> used1,used2;
vector<int> order;
void dfs1(int v) {
    used1[v] = true;
    for (auto u : adj[v])
        if (!used1[u.first])
            dfs1(u.first);
    order.push_back(v);
}

bool dfs2(int v) {
    used2[v] = true;
    for (auto u : adj_rev[v])
        if (used1[u] and !used2[u])
            return true;
    return false;
}

variant<bool,vector<int>> find_journey( int n, int m, vector<int> u, vector<int> v) {
    adj.resize(n); used.resize(n); used1.resize(n); used2.resize(n); adj_rev.resize(n);
    for (int i=0;i<m;i+=2) {
        adj[u[i]].push_back({v[i],i});
        adj_rev[v[i]].push_back(u[i]);
    }
    bool lp = false;
    dfs1(0);
    reverse(order.begin(), order.end());
    for (auto u: order) {
        if (dfs2(u)) {
            lp = true;
            cout << u << " ";
            break;
        }
    }
    if (!lp) {
        return false;
    }
    dfs(0);
    vector<int> route,cycle;
    bool inroute = true;
    for (int i=0;i<path.size();i++) {
        if (u[path[i]] == loop) {
            inroute = false;
        }
        if (inroute) {
            route.push_back(path[i]);
        } else {
            cycle.push_back(path[i]);
        }
    }
    int lenc = cycle.size();
    vector<int> p1=route,b1=route,c1=cycle,d1=cycle,c2(lenc),d2;
    reverse(b1.begin(),b1.end()); reverse(d1.begin(),d1.end());
    for (int i=0;i<lenc;i++) {
        c2[i] = c1[i]^1;
    }
    d2 = c2;
    reverse(d2.begin(),d2.end());
    vector<int> ans;
    ans.insert(ans.end(),p1.begin(),p1.end());
    ans.insert(ans.end(),c1.begin(),c1.end());
    ans.insert(ans.end(),c2.begin(),c2.end());
    ans.insert(ans.end(),d1.begin(),d1.end());
    ans.insert(ans.end(),d2.begin(),d2.end());
    ans.insert(ans.end(),b1.begin(),b1.end());
    
    /*for (auto u: p1) cout << u << " "; cout << "\n";
    for (auto u: c1) cout << u << " "; cout << "\n";
    for (auto u: c2) cout << u << " "; cout << "\n";
    for (auto u: d1) cout << u << " "; cout << "\n";
    for (auto u: d2) cout << u << " "; cout << "\n";
    for (auto u: b1) cout << u << " "; cout << "\n";*/
    return ans;
}

Compilation message (stderr)

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:70:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   70 |     for (int i=0;i<path.size();i++) {
      |                  ~^~~~~~~~~~~~

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