Submission #703152

#	Time	Username	Problem	Language	Result	Execution time	Memory
703152		Dan4Life	Port Facility (JOI17_port_facility)	C++17	0 / 100	1 ms	340 KiB

port_facility

#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define int long long
#define all(a) a.begin(),a.end()
#define rank rank_
const int mxN = (int)2e6+2;
const int MOD = (int)1e9+7;
int n, a[mxN], SZ, cnt[mxN], rank[mxN], bipartite[mxN];
pair<int,int> parent[mxN];

void make_set(int v) {
    parent[v] = make_pair(v, 0);
    rank[v] = 0;
    bipartite[v] = true;
}

pair<int, int> find_set(int v) {
    if (v != parent[v].first) {
        int parity = parent[v].second;
        parent[v] = find_set(parent[v].first);
        parent[v].second ^= parity;
    }
    return parent[v];
}

void unionSet(int a, int b) {
    pair<int, int> pa = find_set(a);
    a = pa.first;
    int x = pa.second;

    pair<int, int> pb = find_set(b);
    b = pb.first;
    int y = pb.second;

    if (a == b) {
        if (x == y)
            bipartite[a] = false;
    } else {
        if (rank[a] < rank[b])
            swap (a, b); SZ--;
        parent[b] = make_pair(a, x^y^1);
        bipartite[a] &= bipartite[b];
        if (rank[a] == rank[b])
            ++rank[a];
    }
}

bool is_bipartite(int v) {
    return bipartite[find_set(v).first];
}

int poww(int a, int b){
    if(!b) return 1;
    int x = poww(a,b/2);
    x*=x,x%=MOD;
    if(b&1)x*=a,x%=MOD;
    return x;
}

int32_t main()
{
    ios_base::sync_with_stdio(false); cin.tie(0);
    cin >> n; SZ=n;
    for(int i = 0; i < n; i++) make_set(i);
    for(int i = 0; i < n; i++){
        int x, y; cin >> x >> y;
        a[x]=a[y]=i;
    }
    set<pair<int,int>> S;
    for(int i = 1; i <= 2*n; i++){
        if(cnt[a[i]]){
            S.erase({cnt[a[i]],a[i]});
            auto itr = S.lower_bound(make_pair(cnt[a[i]],-1));
            while(itr!=S.end()){
                if(find_set(itr->se)==find_set(a[i])) break;
                unionSet(itr->se,a[i]);
                if(!is_bipartite(itr->se) or !is_bipartite(a[i])) { cout << 0; return 0; }
                itr++;
            }
        }
        else S.insert({i,a[i]}),cnt[a[i]]=i;
    }
    cout << poww(2,SZ);
}

Compilation message (stderr)

port_facility.cpp: In function 'void unionSet(long long int, long long int)':
port_facility.cpp:43:9: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
   43 |         if (rank[a] < rank[b])
      |         ^~
port_facility.cpp:44:26: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
   44 |             swap (a, b); SZ--;
      |                          ^~

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