Submission #956036

#	Time	Username	Problem	Language	Result	Execution time	Memory
956036		shezitt	Papričice (COCI20_papricice)	C++17	15 / 110	3 ms	8028 KiB

papricice

#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#include <cassert>

using namespace std;

using ll = long long;

#define int ll
#define fore(i, a, b) for(int i=a; i<b; ++i)
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define pb(x) push_back(x)
#define vi vector<int>

const int N = 2e5+5;

vi adj[N];

int n;

/*int taken[N];

int dfs(int x, int prev=-1){
    int tam = 1;

    for(int child : adj[x]){
        if(child == prev) continue;
        tam += dfs(child, x);
    }

    if(taken[x]){

        taken[x] = tam;

        tam = 0;
    }   

    return tam;

}*/

int tam[N];
int pa[N];

void dfs(int x, int prev=-1){
    tam[x] = 1;
    pa[x] = prev;
    for(int child : adj[x]){
        if(child == prev) continue;
        dfs(child, x);
        tam[x] += tam[child];
    }
}

int f(int x, set<int> &A, set<int> &B, int pre=-1){

    // A -> Es ancestro
    // B -> No es ancestro

    assert(B.count(tam[x]));
    B.erase(tam[x]);

    int res = 1e9;

    // primer caso
    if(A.lower_bound((n+tam[x])/2) != A.end()){
        int p = *A.lower_bound((n + tam[x]) / 2);
        res = min(res, max({tam[x], p-tam[x], n-p}) - min({tam[x], p-tam[x], n-p}));
    }
    if(A.lower_bound((n + tam[x]) / 2) != A.begin()){
        int p = *prev(A.lower_bound((n + tam[x])/2));
        res = min(res, max({tam[x], p-tam[x], n-p}) - min({tam[x], p-tam[x], n-p}));
    }

    // segundo caso
    if(B.lower_bound((n - tam[x])/2) != B.end()){
        int q = *B.lower_bound((n - tam[x]) / 2);
        res = min(res, max({tam[x], q, n-tam[x]-q}) - min({tam[x], q, n-tam[x]-q}));
    }
    if(B.lower_bound((n - tam[x])/2) != B.begin()){
        int q = *prev(B.lower_bound((n - tam[x]) / 2));
        res = min(res, max({tam[x], q, n-tam[x]-q}) - min({tam[x], q, n-tam[x]-q}));
    }

    A.insert(tam[x]);
    for(int child : adj[x]){
        if(child == pre) continue;
        res = min(res, f(child, A, B, x));
        assert(A.count(tam[x]));
    }

    A.erase(tam[x]);
    B.insert(tam[x]);

    return res;

}

// set<pair<int,int>> parientes;

// void calcParientes(int start, int x, int prev=-1){
//     if(start != x){
//         parientes.insert(make_pair(min(start, x), max(start, x)));
//     }
//     for(int child : adj[x]){
//         if(child == prev) continue;
//         calcParientes(start, child, x);
//     }
// }

signed main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    cin >> n;
/*
    if(n <= 200){
        fore(i, 0, n-1){
            int u, v;
            cin >> u >> v;
            adj[u].pb(v);
            adj[v].pb(u);
        }

        int ans = 1e9;

        taken[1] = 1;

        for(int i=2; i<=n; ++i){
            for(int j=i+1; j<=n; ++j){
                taken[1] = taken[i] = taken[j] = 1;

                dfs(1);
                ans = min(ans, max({taken[1],taken[i],taken[j]}) - min({taken[1],taken[i],taken[j]}));

                taken[1] = taken[i] = taken[j] = 0;
            }
        }

        cout << ans;

        return 0;

    }
*/
/*
    if(n <= 2000){

        fore(i, 0, n-1){
            int u, v;
            cin >> u >> v;
            adj[u].pb(v);
            adj[v].pb(u);
        }

        int ans = 1e9;

        dfs(1);

        fore(i, 1, n+1){
            calcParientes(i, i, pa[i]);
        }

        fore(i, 2, n+1){
            fore(j, i+1, n+1){

                int p = i;
                int q = j;

                if(tam[p] > tam[q]) swap(p, q);

                int tam1 = tam[p];
                int tam2 = tam[q];
                if(parientes.count({min(p, q), max(p, q)})){
                    tam2 -= tam1;
                }
                int tam3 = n - tam1 - tam2;

                ans = min(ans, max({tam1, tam2, tam3}) - min({tam1, tam2, tam3}));

            }
        }

        cout << ans;

        return 0;
    }
*/

    // complete task

    fore(i, 0, n-1){
        int u, v;
        cin >> u >> v;
        adj[u].pb(v);
        adj[v].pb(u);
    }

    dfs(1);

    set<int> A, B;
    fore(i, 2, n+1){
        B.insert(tam[i]);
    }

    A.insert(tam[1]);


    int ans = 1e9;
    for(int child : adj[1]){
        ans = min(ans, f(child, A, B, 1));
    }

    cout << ans;

}

• Subtask 1: 15 / 15
• Subtask 2: 0 / 35
• Subtask 3: 0 / 60