Submission #594289

#	Time	Username	Problem	Language	Result	Execution time	Memory
594289		Bench0310	Race (IOI11_race)	C++17	100 / 100	857 ms	114888 KiB

race

#include <bits/stdc++.h>
#include "race.h"

using namespace std;
typedef long long ll;

const int N=200000;
const int K=1000000;
vector<array<int,2>> v[N];
int root=-1;
int sz[N];
int c[N][18];
ll d[N][18];
int lvl[N];
bool vis[N];
vector<int> ch[N];
vector<int> st[N];
int best[K+1];
int res=N;
int k;

void chmin(int &a,int b){a=min(a,b);}

void find_sz(int a,int p)
{
    sz[a]=1;
    for(auto [to,l]:v[a])
    {
        if(to==p||vis[to]) continue;
        find_sz(to,a);
        sz[a]+=sz[to];
    }
}

int find_centroid(int a,int p,int n)
{
    for(auto [to,l]:v[a]) if(to!=p&&!vis[to]&&sz[to]>n/2) return find_centroid(to,a,n);
    return a;
}

void find_d(int a,int p,int level)
{
    for(auto [to,l]:v[a])
    {
        if(to==p||vis[to]) continue;
        c[to][level]=c[a][level]+1;
        d[to][level]=d[a][level]+l;
        find_d(to,a,level);
    }
}

void build_cd(int a,int p)
{
    find_sz(a,-1);
    int centroid=find_centroid(a,-1,sz[a]);
    lvl[centroid]=(p!=-1?lvl[p]+1:0);
    if(p!=-1) ch[p].push_back(centroid);
    else root=centroid;
    find_d(centroid,-1,lvl[centroid]);
    vis[centroid]=1;
    for(auto [to,l]:v[centroid]) if(!vis[to]) build_cd(to,centroid);
}

void go(int a)
{
    st[a].push_back(a);
    for(int b:ch[a])
    {
        go(b);
        for(int to:st[b]) st[a].push_back(to);
    }
    int l=lvl[a];
    best[0]=0;
    for(int b:ch[a])
    {
        for(int to:st[b]) if(d[to][l]<=k&&best[k-d[to][l]]!=-1) chmin(res,c[to][l]+best[k-d[to][l]]);
        for(int to:st[b]) if(d[to][l]<=k&&(best[d[to][l]]==-1||c[to][l]<best[d[to][l]])) best[d[to][l]]=c[to][l];
    }
    for(int x:st[a]) if(d[x][l]<=k) best[d[x][l]]=-1;
}

int best_path(int n,int tk,int h[][2],int l[])
{
    for(int i=0;i<n-1;i++)
    {
        int a=h[i][0],b=h[i][1],w=l[i];
        v[a].push_back({b,w});
        v[b].push_back({a,w});
    }
    k=tk;
    build_cd(0,-1);
    memset(best,255,sizeof(best));
    go(root);
    if(res==N) res=-1;
    return res;
}

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