Submission #505297

#	Time	Username	Problem	Language	Result	Execution time	Memory
505297		wiwiho	Love Polygon (BOI18_polygon)	C++14	100 / 100	225 ms	24152 KiB

polygon

#include <bits/stdc++.h>

#define eb emplace_back
#define mp make_pair
#define F first
#define S second
#define printv(a, b) { \
    for(auto pv : a) b << pv << " "; \
    b << "\n"; \
}

using namespace std;

using pii = pair<int, int>;

const int MAX = 1e9;

map<string, int> id;
int num = 1;
int getid(string& s){
    if(id.find(s) == id.end()) id[s] = num++;
    return id[s];
}

int n;
vector<vector<int>> g;
vector<int> dp0, dp1;
vector<bool> vst, vst2;
vector<int> f;

void init(){
    g.resize(n + 1);
    dp0.resize(n + 1);
    dp1.resize(n + 1);
    vst.resize(n + 1);
    vst2.resize(n + 1);
    f.resize(n + 1);
}

void dfs(int now){
    vst[now] = true;
    int sum = 0, mn = n;
    int cnt = 0;
    for(int i : g[now]){
        if(vst2[i]) continue;
        dfs(i);
        cnt++;
        sum += dp1[i];
        mn = min(mn, dp0[i] - dp1[i]);
    }
    if(cnt == 0){
        dp0[now] = 0; dp1[now] = 1;
    }
    else{
        dp0[now] = sum;
        dp1[now] = sum + mn + 1;
    }
}

int solve(int s){
    //cerr << "solve\n";
    
    while(!vst[s]){
        vst[s] = true;
        s = f[s];
    }

    vector<int> cy;
    int v = s;
    do{
        vst2[v] = vst[v] = true;
        cy.eb(v);
        v = f[v];
    }
    while(v != s);
    //printv(cy, cerr);

    for(int i : cy) dfs(i);

    vector<vector<int>> dps(3, vector<int>(3, MAX));
    dps[0][0] = dp0[cy[0]];
    dps[1][1] = dp0[cy[0]] + 1;
    dps[2][2] = dp1[cy[0]];

    for(int i = 1; i < cy.size(); i++){
        int now = cy[i];
        vector<vector<int>> dps2(3, vector<int>(3, MAX));
        
        for(int fst = 0; fst < 3; fst++){
            dps2[fst][0] = min(dps[fst][1], dps[fst][2]) + dp0[now];
            dps2[fst][1] = min({dps[fst][0], dps[fst][1], dps[fst][2]}) + dp0[now] + 1;
            dps2[fst][2] = min(dps[fst][1], dps[fst][2]) + dp1[now];
        }

        dps = dps2;
    }

    int ans = MAX;
    ans = min({ans, dps[0][1], dps[0][2]});
    ans = min({ans, dps[1][0], dps[1][1], dps[1][2]});
    ans = min({ans, dps[2][1], dps[2][2]});
    if(cy.size() == 2) ans = min(ans, dp0[cy[0]] + dp0[cy[1]]);
    //cerr << "solve ok " << ans << "\n";
    return ans;
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    cin >> n;
    init();

    for(int i = 1; i <= n; i++){
        string s, t;
        cin >> s >> t;
        int u = getid(s), v = getid(t);
        f[u] = v;
    }
    for(int i = 1; i <= n; i++){
        g[f[i]].eb(i);
    }
    //for(auto& i : id) cerr << i.F << " " << i.S << "\n";

    if(n % 2){
        cout << "-1\n";
        return 0;
    }

    int ans = 0;
    for(int i = 1; i <= n; i++){
        if(vst[i]) continue;
        ans += solve(i);
    }

    //printv(dp0, cerr);
    //printv(dp1, cerr);

    cout << ans << "\n";

    return 0;
}

Compilation message (stderr)

polygon.cpp: In function 'int solve(int)':
polygon.cpp:85:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   85 |     for(int i = 1; i < cy.size(); i++){
      |                    ~~^~~~~~~~~~~

• Subtask 1: 21 / 21
• Subtask 2: 25 / 25
• Subtask 3: 29 / 29
• Subtask 4: 25 / 25