Submission #1173137

#	Time	Username	Problem	Language	Result	Execution time	Memory
1173137		thanhvo	Park (BOI16_park)	C++20	0 / 100	3 ms	2632 KiB

park

// Author : Thao Nguyen Xinh 
// Codeforces Handle : thaonguyendethuongvai
// Greedy problem
#include<bits/stdc++.h> 
using namespace std; 
#define fi first 
#define se second
#define endl "\n"
#define pair pair< tn, tn >  
#define tn long long 
#define thaonguyen( i, a, b ) for( tn i = a; i <= b; i++ ) 
#define nguyenthao( i, a, b ) for( tn i = a; i >= b; i-- ) 
#define thaonguyenxinh ios::sync_with_stdio(0); cin.tie(0); cout.tie(0); 
const tn N = 1e5 + 5; 
bool ed[N]; 
set< pair > st; 
vector<tn> g[N]; 
vector<pair> vertex;
tn n, m, u, v, cur_result, cur_min, par[N], sz[N], result = -1, deg[N]; 
tn acs( tn u ){
    return u == par[u] ? u : par[u] = acs( par[u] ); 
}
void join( tn u, tn v ){
    tn x = acs(u); 
    tn y = acs(v);
    if ( sz[x] < sz[y] ) 
        swap( x, y ); 
    if ( x != y ){
        par[x] = y; 
        sz[y] += sz[x];
    }
    result = max( result, cur_min * sz[y] );  
}
signed main(){
    thaonguyenxinh 
    freopen( "thao_nguyen_trong_tim_toan.inp", "r", stdin ); 
    freopen( "thao_nguyen_trong_tim_toan.out", "w", stdout );
    cin >> n >> m; 
    thaonguyen( i, 1, n ) 
        par[i] = i, 
         sz[i] = 1; 
    thaonguyen( i, 1, m ) 
        cin >> u >> v, 
        g[u].push_back(v), 
        g[v].push_back(u),
        deg[u]++, deg[v]++;
    thaonguyen( i, 1, n ) 
        st.insert( { deg[i], i } ); 
    while ( !st.empty() ){
        pair cur = *st.begin(); 
        for ( auto v : g[cur.se] ){
            pair temp = { deg[v], v }; 
            if ( st.find( temp ) != st.end() ){
                st.erase( st.find( temp ) );
                deg[v]--; 
                st.insert( { deg[v], v }  );
            } 
        }
        vertex.push_back( { cur.se, cur.fi } ); 
        st.erase( st.find(cur) ); 
    }
    reverse( vertex.begin(), vertex.end() ); 
    for ( auto u : vertex ){
        cur_min  = u.se;
        ed[u.fi] = true; 
        for ( auto v : g[u.fi] ) 
            if ( ed[v] ) 
                join( u.fi, v ); 
    }
    cout << result;
}

Compilation message (stderr)

park.cpp: In function 'int main()':
park.cpp:36:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   36 |     freopen( "thao_nguyen_trong_tim_toan.inp", "r", stdin );
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
park.cpp:37:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   37 |     freopen( "thao_nguyen_trong_tim_toan.out", "w", stdout );
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 27
• Subtask 2: 0 / 31
• Subtask 3: 0 / 42