Submission #1221955

#	Time	Username	Problem	Language	Result	Execution time	Memory
1221955		lamlamlam	경주 (Race) (IOI11_race)	C++20	100 / 100	395 ms	33516 KiB

race

#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define task "sus"
#define pii pair<int,int>
const int MN = 2e5+5,inf = 1e9,MX = 1e6+5;
vector<pii> adj[MN];
int cnt_child[MN],res = inf,k;
bool del[MN];
void find_cnt_child(int u,int p)
{
    cnt_child[u] = 1;
    for(auto e:adj[u]){
        int v = e.first;
        if(v!=p and !del[v]){
            find_cnt_child(v,u);
            cnt_child[u] += cnt_child[v];
        }
    }
}
int find_centroid(int u,int p,int n)
{
    for(auto e:adj[u]){
        int v = e.first;
        if(v!=p and !del[v] and cnt_child[v]>n/2)
            return find_centroid(v,u,n);
    }
    return u;
}
int dist[MN],best_dist[MX],h[MN];
void dfs1(int u,int p,bool sta)
{
    if(sta){
        if(dist[u]==k) res = min(res,h[u]);
        if(dist[u]<k and best_dist[k-dist[u]])
            res = min(res,best_dist[k-dist[u]]+h[u]);
    }
    else{
        if(dist[u]<=k) {
            if(best_dist[dist[u]]==0) best_dist[dist[u]] = h[u];
            else best_dist[dist[u]] = min(best_dist[dist[u]],h[u]);
        }
    }
    for(auto e:adj[u]){
        int v = e.first;
        int w = e.second;
        if(del[v] or v==p) continue;
        h[v] = h[u]+1;
        dist[v] = dist[u] + w;
        dfs1(v,u,sta);
    }
}
void dfs2(int u,int p)
{
    if(dist[u]<=k) {
        best_dist[dist[u]] = 0;
        dist[u] = 0;
    }
    for(auto e:adj[u]) if(!del[e.first] and e.first!=p) dfs2(e.first,u);
}
void upd_ans(int u)
{
    dist[u] = 0;
    for(auto e:adj[u]){
        int v = e.first;
        int w = e.second;
        if(del[v]) continue;
        h[v] = 1;
        dist[v] = w;
        dfs1(v,u,1);
        dfs1(v,u,0);
    }
    dfs2(u,0);
}
void sol(int u)
{
    find_cnt_child(u,0);
    int n = cnt_child[u];
    int root = find_centroid(u,0,n);
    //cerr << "SOLVING: " << u << ' ' << root << ' ' << n << endl;
    del[root] = 1;
    upd_ans(root);
    //cerr << "ANS: " << res << endl;
    for(auto e:adj[root]) if(!del[e.first]) sol(e.first);
}

int best_path(int n,int K,int h[][2],int l[])
{
    k = K;
    for(int i=0; i<n-1; i++){
        int u,v;
        u = h[i][0]; v = h[i][1];
        adj[u].push_back({v,l[i]});
        adj[v].push_back({u,l[i]});
    }
    sol(0);
    if(res!=inf) return res;
    return -1;
}
//
//signed main()
//{
//    ios_base::sync_with_stdio(false);
//    cin.tie(NULL);
//    if(fopen(task".inp","r")){
//        freopen(task".inp","r",stdin);
//        freopen(task".out","w",stdout);
//    }
//    int n,k,h[MN][2],l[MN];
//    cin >> n >> k;
//    for(int i=0; i<n-1; i++) cin >> h[i][0] >> h[i][1];
//    for(int i=0; i<n-1; i++) cin >> l[i];
//    cout << best_path(n,k,h,l);
//    cerr << "\nTIME: " << clock() << '\n';
//}

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 22 / 22
• Subtask 4: 57 / 57