Submission #901665

#	Time	Username	Problem	Language	Result	Execution time	Memory
901665		MarwenElarbi	Valley (BOI19_valley)	C++17	100 / 100	277 ms	43092 KiB

valley

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define vi vector<int>
#define ve vector
#define ll long long
#define vl vector<ll>
#define vll vector<pair<ll,ll>>
#define onbit __builtin_popcount
#define ii pair<int,int>
#define vvi vector<vi>
#define vii vector<ii>
#define gii greater<ii>
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define INF 1e18
#define eps 1e-7
#define eps1 1e-2
#define optimise ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define MAX_A 1e5+5
using namespace std;
using namespace __gnu_pbds;
template <class T>
using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
const ll MOD = 1e9+7;
const int nax = 1e5+5;
const int MAX_VAL = 1e6+1;
double PI=3.14159265359;
int arx[8]={1,0,0,-1,-1,-1, 1, 1};
int ary[8]={0,1,-1, 0, 1,-1,-1, 1};
void setIO(string s) {
    freopen((s + ".in").c_str(), "r", stdin);
    freopen((s + ".out").c_str(), "w", stdout);
}
int n,s,q,e;
vii adj[nax];
bool shop[nax];
long long dp[nax];
long long dis[nax];
pair<int,int> euler[nax];
int timer=-1;
int parent[nax][20];
long long cnt[nax][20];
int depth[nax];
void euler_tour(int x,int p)
{
    timer++;
    euler[x].fi=timer;
    for(auto u:adj[x]){
        if(u.fi==p) continue;
        depth[u.fi]=depth[x]+1;
        dis[u.fi]=dis[x]+u.se;
        parent[u.fi][0]=x;
        euler_tour(u.fi,x);
    }
    euler[x].se=timer;
    return;
}
void dfs(int x,int p)
{
    if(adj[x].size()==1&&x!=e){
        if(shop[x]) dp[x]=0;
        else dp[x]=1e15;
        return;
    }
    dp[x]=1e15;
    for(auto u:adj[x]){
        if(u.fi==p) continue;
        dfs(u.fi,x);
        dp[x]=min(dp[x],dp[u.fi]+u.se);
    }
    if(shop[x]) dp[x]=0;
    return;
}
void jumps(int x,int p)
{
    cnt[x][0]=min(dp[x],dp[parent[x][0]]);
    for (int i = 1; i < 20; ++i)
    {
        parent[x][i]=parent[parent[x][i-1]][i-1];
        cnt[x][i]=min(cnt[x][i-1],cnt[parent[x][i-1]][i-1]);
        //if(x==0) cout <<cnt[x][i]<<" "<<cnt[x][i-1]<<" "<<cnt[parent[x][i-1]][i-1]<<" "<<parent[x][i]<<endl;
    }
    //if(x==9) for(auto u:adj[x]) cout <<u.fi<<endl;
    for(auto u:adj[x]){
        if(u.fi==p) continue;
        jumps(u.fi,x);
    }
}
int main(){
    optimise;
    /*#ifndef ONLINE_JUDGE
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif*/
    cin>>n>>s>>q>>e;
    e--;
    parent[e][0]=e;
    dis[e]=0;
    depth[e]=0;
    pair<int,int> edges[n-1];
    for (int i = 0; i < n-1; ++i)
    {
        int x,y,z;
        cin>>x>>y>>z;
        x--;y--;
        edges[i]={x,y};
        adj[x].pb({y,z});
        adj[y].pb({x,z});
    }
    euler_tour(e,-1);
    for (int i = 0; i < s; ++i)
    {
        int x;
        cin>>x;
        x--;
        shop[x]=true;
    }
    dfs(e,-1);
    for (int i = 0; i < n; ++i)
    {
        dp[i]-=dis[i];
    }
    jumps(e,-1);
    while(q--){
        int i,r;
        cin>>i>>r;
        i--,r--;
        int a=edges[i].fi;
        int b=edges[i].se;
        if(euler[a].fi>euler[b].fi) swap(a,b);
        //cout <<euler[b].fi<<" "<<euler[b].se<<" "<<euler[r].fi<<endl;
        if(euler[b].fi<=euler[r].fi&&euler[r].se<=euler[b].se){
            int d=depth[r]-depth[b];
            //cout <<dp[r]<<" "<<dis[r]<<endl;
            long long res=dp[r];
            int lst=r;
            //cout <<d<<endl;
            for (int i = 19; i >= 0; --i)
            {
                if(d&(1<<i)){
                    res=min(res,cnt[lst][i]);
                    lst=parent[lst][i];
                }
            }//cout <<res<<" "<<lst<<endl;
            if(shop[r]){
                cout <<0<<endl;
            }
            else if(res>=1e14){
                cout <<"oo"<<endl;
            }else{
                //cout <<res<<" "<<dis[r]-dis[b]+1<<endl;
                cout<<dis[r]+res<<endl;
            }
        }else cout <<"escaped"<<endl;
    }
}

Compilation message (stderr)

valley.cpp: In function 'void setIO(std::string)':
valley.cpp:35:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   35 |     freopen((s + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
valley.cpp:36:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   36 |     freopen((s + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 27 / 27
• Subtask 3: 23 / 23
• Subtask 4: 41 / 41