Submission #1197775

#	Time	Username	Problem	Language	Result	Execution time	Memory
1197775		Zbyszek99	Mousetrap (CEOI17_mousetrap)	C++20	45 / 100	844 ms	68076 KiB

mousetrap

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define ld long double
#define ull unsigned long long
#define ff first
#define ss second
#define pii pair<int,int>
#define pll pair<long long, long long>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace __gnu_pbds;
using namespace std;
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;
//mt19937 mt;void random_start(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll los(ll a, ll b) {return a + (mt() % (b-a+1));}
const int INF = 1e9+50;
const ll INF_L = 1e18+40;
const ll MOD = 1e9+7;

vi graph[1000001];
int tdist[1000001];
int ans[1000001];
int dp[1000001];
int n,t,m;

void dfs_tdist(int v, int pop, int d, int cur_ans = 0)
{
    tdist[v] = d++;
    cur_ans += siz(graph[v])-2;
    if(siz(graph[v]) == 1) cur_ans++;
    if(v == pop)  cur_ans = 0;
    ans[v] = cur_ans;
    forall(it,graph[v])
    {
        if(it != pop) 
        {
            dfs_tdist(it,v,d,cur_ans);
        }
    }
}

void dfs_mdist(int v, int pop, int min_dep)
{
    min_dep = min(min_dep,tdist[v]);
    ans[v] += tdist[v] - min_dep;
    forall(it,graph[v])
    {
        if(it != pop)
        {
            dfs_mdist(it,v,min_dep);
        }
    }
}

void dfs(int v, int pop, int cur = 1, int cur_add = 0, int d = 0)
{
    vi best;
    int my_cur = cur;
    if((v == pop && siz(graph[v]) == 1) || (v != pop && siz(graph[v]) == 2)) cur++;
    else cur = max(1,cur-siz(graph[v])*2);
    forall(it,graph[v])
    {
        if(it != pop)
        {
            int new_add = cur_add;
            if(tdist[m] - tdist[it] == d+1) new_add += min(max(0,(v != pop ? siz(graph[v])-2 : siz(graph[v])-1)),cur);
            dfs(it,v,cur,new_add,d+1);
            best.pb(dp[it]);
        }
    }
    sort(all(best));
    reverse(all(best));
    cur = my_cur;
    if(siz(best) >= cur+1)
    {
        dp[v] = best[cur];
    }
    else if(siz(best) >= 1)
    {
        forall(it,best)
        {
            dp[v] = min(ans[v]+cur_add + (tdist[m] - tdist[v] != d ? (siz(graph[v]) != 1 ? max(1,siz(graph[v])-2) : 0) : 0), it);
        }
    }
    else
    {
        dp[v] = ans[v] + cur_add + (tdist[m] - tdist[v] != d ? (siz(graph[v]) != 1 ? max(1,siz(graph[v])-2) : 0) : 0);
    }
    if(v == t)
    {
        dp[v] = ans[m] + cur_add;
    }
}

int main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    //random_start();
    cin >> n >> t >> m;
    rep(i,n-1)
    {
        int a,b;
        cin >> a >> b;
        graph[a].pb(b);
        graph[b].pb(a);
    }
    dfs_tdist(t,t,0);
    dfs_mdist(m,m,tdist[m]);
    dfs(m,m);
    cout << dp[m] << "\n";
}

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