Submission #217494

#	Time	Username	Problem	Language	Result	Execution time	Memory
217494		Autoratch	Race (IOI11_race)	C++14	21 / 100	3089 ms	211192 KiB

race

#include "race.h"
#include <bits/stdc++.h>
using namespace std;

const int N = 2e5 + 1;
const int K = 20;

int n,k,cn;
vector<pair<int,int> > adj[N];
vector<int> cen[N];
int sz[N],pa[N],lv[N],dp[K][N],ans = INT_MAX;
bool blocked[N];
long long dist[N];
unordered_map<int,int> res[N],lc[N];

void dfs(int u,int p){ sz[u] = 1; for(auto [d,v] : adj[u]) if(v!=p and !blocked[v]) dfs(v,u),sz[u]+=sz[v]; }

void build(int u,int cp)
{
    dfs(u,0);
    int c = u,prev = 0;
    while(true)
    {
        int mx = 0,id = 0;
        for(auto [d,v] : adj[c]) if(!blocked[v] and v!=prev) if(sz[v]>mx) mx = sz[v],id = v;
        if(mx*2>sz[u]) prev = c,c = id;
        else break;
    }
    if(cp==0) cn = c;
    pa[c] = cp;
    if(cp) cen[cp].push_back(c);
    blocked[c] = true;
    for(auto [d,v] : adj[c]) if(!blocked[v]) build(v,c);
}

void dfslca(int u,int p){ lv[u] = lv[p]+1,dp[0][u] = p; for(auto [d,v] : adj[u]) if(v!=p) dist[v] = dist[u]+(long long)d,dfslca(v,u); }

int lca(int a,int b)
{
    if(lv[a]<lv[b]) swap(a,b);
    for(int i = K-1;i >= 0;i--) if(lv[dp[i][a]]>=lv[b]) a = dp[i][a];
    if(a==b) return a;
    for(int i = K-1;i >= 0;i--) if(dp[i][a]!=dp[i][b]) a = dp[i][a],b = dp[i][b];
    return dp[0][a];
}

void upd(int u,int p,bool f)
{
    int l;
    if(lc[u][p]) l = lc[u][p];
    else l = lc[u][p] = lca(u,p);
    long long all = dist[u]-dist[l]+dist[p]-dist[l];
    if(all>k) return;
    int len = lv[u]-lv[l]+lv[p]-lv[l];
    if(!f)
    {
        if(all==k) ans = min(ans,len);
        else if(res[p][k-all]) ans = min(ans,res[p][k-all]+len);
    }
    else if(res[p][all]==0 or res[p][all]>len) res[p][all] = len;
}

void sol(int c,int u,int t)
{
    upd(u,c,t);
    for(int v : cen[u]) sol(c,v,t);
}

void run(int u)
{
    for(int v : cen[u])
    {
        sol(u,v,0);
        sol(u,v,1);
    }
    for(int v : cen[u]) run(v);
}

int best_path(int nn,int kk,int h[][2],int l[])
{
    n = nn,k = kk;
    for(int i = 0;i < n-1;i++)
    {
        int a = h[i][0],b = h[i][1],d = l[i]; a++,b++;
        adj[a].push_back({d,b});
        adj[b].push_back({d,a});
    }
    build(1,0);
    dfslca(1,0);
    for(int i = 1;i < K;i++) for(int j = 1;j <= n;j++) dp[i][j] = dp[i-1][dp[i-1][j]];
    run(cn);
    if(ans==INT_MAX) ans = -1;
    return ans;
}

Compilation message (stderr)

race.cpp: In function 'void dfs(int, int)':
race.cpp:16:44: warning: decomposition declaration only available with -std=c++1z or -std=gnu++1z
 void dfs(int u,int p){ sz[u] = 1; for(auto [d,v] : adj[u]) if(v!=p and !blocked[v]) dfs(v,u),sz[u]+=sz[v]; }
                                            ^
race.cpp:16:48: warning: unused variable 'd' [-Wunused-variable]
 void dfs(int u,int p){ sz[u] = 1; for(auto [d,v] : adj[u]) if(v!=p and !blocked[v]) dfs(v,u),sz[u]+=sz[v]; }
                                                ^
race.cpp: In function 'void build(int, int)':
race.cpp:25:18: warning: decomposition declaration only available with -std=c++1z or -std=gnu++1z
         for(auto [d,v] : adj[c]) if(!blocked[v] and v!=prev) if(sz[v]>mx) mx = sz[v],id = v;
                  ^
race.cpp:25:22: warning: unused variable 'd' [-Wunused-variable]
         for(auto [d,v] : adj[c]) if(!blocked[v] and v!=prev) if(sz[v]>mx) mx = sz[v],id = v;
                      ^
race.cpp:33:14: warning: decomposition declaration only available with -std=c++1z or -std=gnu++1z
     for(auto [d,v] : adj[c]) if(!blocked[v]) build(v,c);
              ^
race.cpp:33:18: warning: unused variable 'd' [-Wunused-variable]
     for(auto [d,v] : adj[c]) if(!blocked[v]) build(v,c);
                  ^
race.cpp: In function 'void dfslca(int, int)':
race.cpp:36:66: warning: decomposition declaration only available with -std=c++1z or -std=gnu++1z
 void dfslca(int u,int p){ lv[u] = lv[p]+1,dp[0][u] = p; for(auto [d,v] : adj[u]) if(v!=p) dist[v] = dist[u]+(long long)d,dfslca(v,u); }
                                                                  ^

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