Submission #244373

#	Time	Username	Problem	Language	Result	Execution time	Memory
244373		Osama_Alkhodairy	Port Facility (JOI17_port_facility)	C++17	22 / 100	6059 ms	34168 KiB

port_facility

#include <bits/stdc++.h>
using namespace std;
#define finish(x) return cout << x << endl, 0
#define ll long long
 
const int N = 1000001;
 
int n, col[N], p[N], sz[N], vis[N], mod = 1e9 + 7;
vector <pair <int, int> > a;
vector <int> f, v[N];
int vis_id;

void invert(int node){
    if(vis[node] == vis_id) return;
    vis[node] = vis_id;
    col[node] ^= 1;
    for(auto &i : v[node]){
        invert(i);
    }
} 
int find(int x){
    if(p[x] == x) return x;
    return p[x] = find(p[x]);
}
void merge(int x, int y){
    if(col[x] == -1 || col[y] == -1){
        v[x].push_back(y);
        v[y].push_back(x);
        sz[find(x)] += sz[find(y)];
        p[find(y)] = find(x);        
        if(col[x] == -1 && col[y] == -1){
            col[x] = 0;
            col[y] = 1;
            return;
        }
        if(col[x] == -1) swap(x, y);
        col[y] = col[x] ^ 1;
        return;
    }
    if(find(x) == find(y)){
        if(col[x] == col[y]){
            cout << 0 << endl;
            exit(0);
        }
        return;
    }
    if(col[x] == (col[y] ^ 1)){
        v[x].push_back(y);
        v[y].push_back(x);
        sz[find(x)] += sz[find(y)];
        p[find(y)] = find(x);
        return;
    }
    if(sz[find(x)] < sz[find(y)]) swap(x, y);
    vis_id++;
    invert(y);
    assert(col[x] != col[y]);
    v[x].push_back(y);
    v[y].push_back(x);
    sz[find(x)] += sz[find(y)];
    p[find(y)] = find(x);
}
int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    memset(col, -1, sizeof col);
    cin >> n;
    a.resize(n);
    f.resize(2 * n);
    for(int i = 0 ; i < n ; i++){
        cin >> a[i].first >> a[i].second;
        a[i].first--; a[i].second--;
        f[a[i].first] = f[a[i].second] = i;
        p[i] = i;
        sz[i] = 1;
    }
    vector <int> o;
    for(int i = 0 ; i < 2 * n ; i++){
        if(a[f[i]].first == i){
            o.push_back(f[i]);
        }
        else{
            int j = (int)o.size() - 1;
            while(o[j] != f[i]){
                merge(f[i], o[j]);
                j--;
            }
            for(int k = j ; k + 1 < (int)o.size() ; k++){
                o[k] = o[k + 1];
            }
            o.pop_back();
        }
    }
    int ans = 1;
    for(int i = 0 ; i < n ; i++){
        if(find(i) == i){
            ans *= 2;
            if(ans >= mod) ans -= mod;
        }
    }
    cout << ans << endl;
}

• Subtask 1: 10 / 10
• Subtask 2: 12 / 12
• Subtask 3: 0 / 56
• Subtask 4: 0 / 22