Submission #1105242

#	Time	Username	Problem	Language	Result	Execution time	Memory
1105242		alexander707070	Highway Tolls (IOI18_highway)	C++14	90 / 100	215 ms	23876 KiB

highway

#include<bits/stdc++.h>
#define MAXN 200007

#include "highway.h"

using namespace std;

int n,m,dep[MAXN],from,to,st,et,parent[MAXN];
bool ok,li[MAXN];

vector< pair<int,int> > v[MAXN],g[MAXN];
vector<int> euler,euler2;
vector<int> w;

void dfs(int x,int p){

    dep[x]=dep[p]+1;
    parent[x]=p;

    for(int i=0;i<v[x].size();i++){
        if(v[x][i].first==p)continue;

        euler.push_back(v[x][i].second);
        dfs(v[x][i].first,x);
    }
}

void dfss(int x,int p){
    for(int i=0;i<v[x].size();i++){
        if(v[x][i].first==p)continue;

        euler2.push_back(v[x][i].second);
        dfss(v[x][i].first,x);
    }
}

queue<int> q;

void bfs(int x){
    for(int i=0;i<g[x].size();i++){
        if(li[g[x][i].first])continue;

        li[g[x][i].first]=true;
        q.push(g[x][i].first);

        v[x].push_back(g[x][i]);
        v[g[x][i].first].push_back({x,g[x][i].second});
    }
}

void dobfs(int x){
    q.push(x);
    li[x]=true;

    while(!q.empty()){
        bfs(q.front());
        q.pop();
    }
}

long long check(int x){
    for(int i=0;i<m;i++)w[i]=1;

    for(int y=1;y<=x;y++){
        for(int i=0;i<g[y].size();i++){
            w[g[y][i].second]=0;
        }
    }

    return ask(w);
}

long long pref(int x){
    for(int i=0;i<m;i++)w[i]=1;

    for(int i=0;i<=x;i++)w[euler[i]]=0;

    return ask(w);
}

long long pref2(int x){
    for(int i=0;i<m;i++)w[i]=1;

    for(int i=0;i<=x;i++)w[euler2[i]]=0;

    return ask(w);
}

void find_pair(int N, vector<int> U, vector<int> V, int A, int B) {

    n=N; m=int(U.size());
    for(int i=1;i<=m;i++){
        g[U[i-1]+1].push_back({V[i-1]+1,i-1});
        g[V[i-1]+1].push_back({U[i-1]+1,i-1});
    }

    w.resize(m);
    for(int i=0;i<m;i++)w[i]=0;
    long long path=ask(w);

    int l=0,r=n+1,tt;
    while(l+1<r){
        tt=(l+r)/2;
        if(check(tt)==path){
            r=tt;
        }else{
            l=tt;
        }
    }

    dobfs(r);

    dfs(1,0);
    for(int i=1;i<=n;i++){
        reverse(v[i].begin(),v[i].end());
    }
    dfss(1,0);

    l=-1; r=int(euler.size());
    while(l+1<r){
        tt=(l+r)/2;
        if(pref(tt)==path){
            r=tt;
        }else{
            l=tt;
        }
    }
    to=r;

    l=-1; r=int(euler2.size());

    for(int i=0;i<euler2.size();i++){
        if(euler2[i]==euler[to]){
            l=i-1; break;
        }
    }

    while(l+1<r){
        tt=(l+r)/2;
        if(pref2(tt)==path){
            r=tt;
        }else{
            l=tt;
        }
    }
    from=r;

    st=euler2[from]; et=euler[to];

    if(st==et){
        if(dep[U[st]+1]>dep[V[st]+1])swap(U[st],V[st]);

        U[st]++;
        for(int i=0;i<path/A-1;i++)U[st]=parent[U[st]];
        U[st]--;

        answer(U[st],V[st]);
        return;
    }

    if(dep[U[st]+1]>dep[V[st]+1])swap(U[st],V[st]);
    if(dep[U[et]+1]>dep[V[et]+1])swap(U[et],V[et]);

    answer(V[st],V[et]);

    return;
}

Compilation message (stderr)

highway.cpp: In function 'void dfs(int, int)':
highway.cpp:20:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   20 |     for(int i=0;i<v[x].size();i++){
      |                 ~^~~~~~~~~~~~
highway.cpp: In function 'void dfss(int, int)':
highway.cpp:29:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   29 |     for(int i=0;i<v[x].size();i++){
      |                 ~^~~~~~~~~~~~
highway.cpp: In function 'void bfs(int)':
highway.cpp:40:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   40 |     for(int i=0;i<g[x].size();i++){
      |                 ~^~~~~~~~~~~~
highway.cpp: In function 'long long int check(int)':
highway.cpp:65:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   65 |         for(int i=0;i<g[y].size();i++){
      |                     ~^~~~~~~~~~~~
highway.cpp: In function 'void find_pair(int, std::vector<int>, std::vector<int>, int, int)':
highway.cpp:132:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  132 |     for(int i=0;i<euler2.size();i++){
      |                 ~^~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 6 / 6
• Subtask 4: 33 / 33
• Subtask 5: 18 / 18
• Subtask 6: 21 / 31