Submission #1049337

#	Time	Username	Problem	Language	Result	Execution time	Memory
1049337		beaconmc	Race (IOI11_race)	C++14	100 / 100	1534 ms	192536 KiB

race

#include "race.h"
#include <bits/stdc++.h>
 
typedef long long ll;
#define FOR(i,x,y) for(ll i=x; i<y; i++)
#define FORNEG(i,x,y) for(ll i=x; i>y; i--)
 
using namespace std;
 
const ll maxn = 200005;
const ll INF = 1000000000;
 
vector<vector<ll>> edges[maxn];
ll par[maxn];
ll centpar[maxn];
ll depth[maxn];
ll realdepth[maxn];
ll ancc[maxn][20];
bool visited[maxn];
ll sub[maxn];
 
ll anc(ll a, ll x){
    if (a==0) return 0;
    if (x==0) return par[a];
    if (ancc[a][x] != -1) return ancc[a][x];
    return ancc[a][x] = anc(anc(a,x-1),x-1);
}
 
ll lca(ll a, ll b){
    if (depth[a] < depth[b]) swap(a,b);
    FORNEG(i,19,-1) if (depth[anc(a, i)] >= depth[b]) a = anc(a,i);
    if (a==b) return a;
    FORNEG(i,19,-1) if (anc(a,i) != anc(b,i)) a = anc(a,i), b = anc(b,i);
    return par[a];
}
 
void initdfs(ll a,ll p, ll d, ll dd){
    par[a] = p;
    depth[a] = d;
    realdepth[a] = dd;
    for (auto&i : edges[a]){
        if (i[0] != p) initdfs(i[0], a, d+1, dd+i[1]);
    }
}
 
ll centroid(ll root, ll a, ll p){
    for (auto&i : edges[a]){
        if (!visited[i[0]] && i[0] != p && sub[i[0]] > sub[root]/2) return centroid(root, i[0], a);
    }
    return a;
}
void dfs(ll a, ll p){
    sub[a] = 1;
    for (auto&i : edges[a]){
 
        if(i[0] != p && !visited[i[0]]) dfs(i[0], a), sub[a] += sub[i[0]];
    }
}
void build(ll a, ll p){
 
    dfs(a,p);
    ll cent = centroid(a, a, p);
 
 
    centpar[cent] = p;
    visited[cent] = 1;
    for (auto&i : edges[cent]){
        if (!visited[i[0]]) build(i[0], cent);
    }
}
 
vector<array<ll,3>> dists[maxn];
 
int best_path(int N, int K, int H[][2], int L[])
{
    FOR(i,0,maxn) par[i] = -1, centpar[i] = -1, par[i] -1, depth[i] = -1, realdepth[i] = -1,visited[i] = 0,dists[i].clear(),edges[i].clear();
    FOR(i,0,maxn)FOR(j,0,20) ancc[i][j] = -1;
    
    
    FOR(i,0,N-1){
 
        edges[H[i][0]].push_back({H[i][1], L[i]});
        edges[H[i][1]].push_back({H[i][0], L[i]});
    }
 
    
    initdfs(0,-1,0,0);
    dfs(0,-1);
 
    build(0,-1);
 
 
 
    
 
    FOR(i,0,N){
        ll temp = centpar[i];
        ll prev = i;
        ll cnt = 0;
        while (temp != -1){
            cnt++;
 
            ll idk = lca(temp,i);
            ll cur = depth[temp] + depth[i] - depth[idk]*2;
 
           
            ll dist = realdepth[temp] + realdepth[i] - realdepth[idk]*2;
 
            dists[temp].push_back({prev, dist, cur });
            
            prev = temp;
            temp = centpar[temp];
        }
    }
    ll ans = INF;
    ll cnt = 0;
    FOR(i,0,N){

        sort(dists[i].begin(), dists[i].end());
        unordered_map<ll, ll> sus;
        sus[0] = 0;
        vector<array<ll, 3>> cache;
        if (dists[i].size()) cache.push_back(dists[i][0]);

        FOR(j,1,dists[i].size()){
            if (dists[i][j][0] != dists[i][j-1][0]){
                for (auto&k : cache){
                    if (sus.count(k[1])) sus[k[1]] = min(sus[k[1]], k[2]);
                    else sus[k[1]] = k[2];
                }
                cache.clear();
            }
            ll req = K - dists[i][j][1];
            if (sus.count(req)) ans = min(ans, sus[req] + dists[i][j][2]);
            cache.push_back(dists[i][j]);
        }
    }
 
    if (ans >= INF) return -1;
    else return ans;
 
}
 
 
 
 

Compilation message (stderr)

race.cpp: In function 'int best_path(int, int, int (*)[2], int*)':
race.cpp:76:56: warning: right operand of comma operator has no effect [-Wunused-value]
   76 |     FOR(i,0,maxn) par[i] = -1, centpar[i] = -1, par[i] -1, depth[i] = -1, realdepth[i] = -1,visited[i] = 0,dists[i].clear(),edges[i].clear();
      |                                                 ~~~~~~~^~
race.cpp:5:33: warning: comparison of integer expressions of different signedness: 'll' {aka 'long long int'} and 'std::vector<std::array<long long int, 3> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    5 | #define FOR(i,x,y) for(ll i=x; i<y; i++)
......
  125 |         FOR(j,1,dists[i].size()){
      |             ~~~~~~~~~~~~~~~~~~~  
race.cpp:125:9: note: in expansion of macro 'FOR'
  125 |         FOR(j,1,dists[i].size()){
      |         ^~~
race.cpp:116:8: warning: unused variable 'cnt' [-Wunused-variable]
  116 |     ll cnt = 0;
      |        ^~~

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