Submission #417832

#	Time	Username	Problem	Language	Result	Execution time	Memory
417832		egekabas	Mousetrap (CEOI17_mousetrap)	C++14	45 / 100	1022 ms	78540 KiB

mousetrap

#include <bits/stdc++.h>
#define all(x) (x).begin(), (x).end()
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pull;
typedef pair<ll, ll> pii;
typedef pair<ld, ld> pld;
ll n, t, m;
vector<ll> g[1000009];
ll trap[1000009];
ll dp[1000009];
 
ll ans[1000009];   
void dfs(ll v, ll prt){
    if(v == t){
        trap[v] = 1;
        return;
    }
    for(auto u : g[v])
        if(u != prt){
            dfs(u, v);
            if(trap[u])
                trap[v] = 1;
        }
    pii maxi = {0, 0};
    ll edgecnt = 0;
    for(auto u : g[v])
        if(u != prt && trap[u] == 0){
            if(dp[u] >= maxi.ff){
                maxi.ss = maxi.ff;
                maxi.ff = dp[u];
            }
            else if(dp[u] >= maxi.ss)
                maxi.ss = dp[u];
            ++edgecnt;
        }
    dp[v] = edgecnt+maxi.ss;
    ans[v] = edgecnt;
    if(v == m)
        ans[v] += maxi.ss;
    for(auto u : g[v])
        if(u != prt && trap[u]){
            dp[v] += dp[u];
            ans[v] += ans[u];
        }
}
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    
    //freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w", stdout);

    cin >> n >> t >> m;
    for(ll i = 0; i < n-1; ++i){
        ll x, y;
        cin >> x >> y;
        g[x].pb(y);
        g[y].pb(x);
    }
    dfs(m, 0);
    cout << ans[m] << '\n';
}

• Subtask 1: 20 / 20
• Subtask 2: 25 / 25
• Subtask 3: 0 / 20
• Subtask 4: 0 / 35