Submission #1279499

#	Time	Username	Problem	Language	Result	Execution time	Memory
1279499		dhuyyyy	Race (IOI11_race)	C++20	100 / 100	315 ms	34104 KiB

race

#include <bits/stdc++.h>
#include "race.h"
#define fi first
#define se second
using namespace std;

using ii = pair<int,int>;

const int maxn = 2e5+5;
const int maxk = 1e6+5;


int res = 1e9 + 9;

int pos[maxk], sub[maxn];

bool num[maxn];

stack <int> st;

vector <ii> adj[maxn];

void dfs(int u,int p){
    sub[u] = 1;
    for (ii it : adj[u]){
        if (it.fi == p || num[it.fi]) continue;
        dfs(it.fi,u);
        sub[u] += sub[it.fi];
    }
}
int centroid(int u,int p,int n){
    for (ii it : adj[u]){
        if (it.fi == p || num[it.fi]) continue;
        if (sub[it.fi] * 2 > n) return centroid(it.fi,u,n);
    }
    return u;
}
void getans(int u,int p,int cur,int km,int K,int type){
    if (km > K) return;
    if (!type){
        res = min(res,cur + pos[K - km]);
    } else{
        pos[km] = min(pos[km],cur);
        st.push(km);
    }
    for (ii it : adj[u]){
        if (it.fi == p || num[it.fi]) continue;
        getans(it.fi,u,cur + 1,km + it.se,K,type);
    }
}
void solve(int u,int K){
    dfs(u,0);
    int m = sub[u];
    int root = centroid(u,0,m);
    num[root] = 1;
    for (ii it : adj[root]){
        if (num[it.fi]) continue;
        getans(it.fi,root,1,it.se,K,0);
        getans(it.fi,root,1,it.se,K,1);
    }
    while (!st.empty()){
        pos[st.top()] = 1e9 + 9;
        st.pop();
    }
    for (ii it : adj[root]){
        if (num[it.fi]) continue;
        solve(it.fi,K);
    }
}
int best_path(int N, int K, int H[][2], int L[]){
    for (int i = 0; i < N - 1; i++){
        H[i][0]++; H[i][1]++;
        adj[H[i][0]].push_back({H[i][1],L[i]});
        adj[H[i][1]].push_back({H[i][0],L[i]});
    }
    for (int i = 1; i <= K; i++) pos[i] = 1e9 + 9;
    solve(1,K);
    return (res <= 0 || res > N ? -1 : res);
}

#ifdef LOCAL
signed main(){
    ios_base::sync_with_stdio(0); cin.tie(0);

int N = 11, K = 12;
int H[10][2] = {{0,1},{0,2},{2,3},{3,4},{4,5},{0,6},{6,7},{6,8},{8,9},{8,10}};
int L[10] = {3,4,5,4,6,3,2,5,6,7};
    cout << best_path(N, K, H, L) << '\n';

    return 0;
}
#endif // LOCAL

/*
int N = 4, K = 3;
int H[3][2] = {{0,1},{1,2},{1,3}};
int L[3] = {1,2,4};

int N = 3, K = 3;
int H[2][2] = {{0,1},{1,2}};
int L[2] = {1,1};

int N = 11, K = 12;
int H[10][2] = {{0,1},{0,2},{2,3},{3,4},{4,5},{0,6},{6,7},{6,8},{8,9},{8,10}};
int L[10] = {3,4,5,4,6,3,2,5,6,7};
*/

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