Submission #42431

#	Time	Username	Problem	Language	Result	Execution time	Memory
42431		comfile	Race (IOI11_race)	C++11	43 / 100	3051 ms	33276 KiB

race

#include <bits/stdc++.h>
#define mp make_pair
#define pb push_back
using namespace std;
const int MN = 200010;
int n,k,ans,sz[MN],dead[MN];
vector<pair<int,int> > g[MN];
void get_sz(int cur,int prev){
    sz[cur] = 1;
    for(auto &x : g[cur]) if(x.first!=prev && !dead[x.first]){
        get_sz(x.first,cur);
        sz[cur] += sz[x.first];
    }
}
int dfs(int cur,int prev,int tot){
    for(auto &x : g[cur]) if(x.first!=prev && !dead[x.first]){
        if(sz[x.first]>(tot/2)) return dfs(x.first,cur,tot);
    }
    return cur;
}
int one(int root){
    get_sz(root,-1);
    return dfs(root,-1,sz[root]);
}
void rec(int start){
    int c = one(start);
    dead[c] = 1;
    for(auto &x : g[c]) if(!dead[x.first]) rec(x.first);
    map<int,int> cnt;
    function<void (int,int,int,int,int)> add_cnt = [&](int cur,int prev,int d,int st,int add){
        if(d>k) return;
        cnt[d] = cnt[d]?min(cnt[d],st):st;
        for(auto &x : g[cur]) if(x.first!=prev && !dead[x.first]){
            add_cnt(x.first,cur,d+x.second,st+1,add);
        }
    };
    function<void (int,int,int,int)> calc = [&](int cur,int prev,int d,int st){
        if(d>k) return;
        if(k!=d && cnt[k-d]) ans = min(ans,st+cnt[k-d]);
        for(auto &x: g[cur]) if(x.first!=prev && !dead[x.first]){
            calc(x.first,cur,d+x.second,st+1);
        }
    };
    add_cnt(c,-1,0,0,1);
    if(cnt[k]) ans = min(ans,cnt[k]);
    cnt.clear();
    for(auto &x : g[c]) if(!dead[x.first]){
        calc(x.first,c,x.second,1);
        add_cnt(x.first,c,x.second,1,1);
    }
    dead[c] = 0;
}
int best_path(int _n,int _k,int h[][2],int l[]){
    ans = MN;
    n = _n; k = _k;
    for(int i=0;i<n-1;i++){
        int a = h[i][0];
        int b = h[i][1];
        int c = l[i];
        g[a].pb(mp(b,c));
        g[b].pb(mp(a,c));
    }
    rec(0);
    if(ans>=MN) ans = -1;
    return ans;
}

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 22 / 22
• Subtask 4: 0 / 57