Submission #657470

#	Time	Username	Problem	Language	Result	Execution time	Memory
657470		perchuts	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	102 ms	21232 KiB

oneway

#include <bits/stdc++.h>
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
#define endl '\n'
#define _ ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define pb push_back
 
using namespace std;
 
using ii = pair<int,int>;
using iii = tuple<int,int,int>;
using ll = long long;
 
const int inf = 1e9+1;
const int mod = 1e9+7;
const int maxn = 2e5+100;
 
template<typename X,typename Y> bool ckmin(X& x,Y y){return (x>y?x=y,1:0);}
template<typename X,typename Y> bool ckmax(X& x,Y y){return (x<y?x=y,1:0);}
 
vector<ii>g[maxn];
 
int dp[maxn], lvl[maxn], entrada[maxn], saida[maxn], bridge[maxn], vis[maxn], t = 0;
ii ranges[maxn][2];
 
void dfs(int u,int p){
    lvl[u] = lvl[p] + 1, entrada[u] = ++t;
    for(auto [v,idx]:g[u]){
        if(!lvl[v]){
            dfs(v,u);
            dp[u] += dp[v];
        }
        else if(lvl[u]<lvl[v]) --dp[u];
        else if(lvl[u]>lvl[v]) ++dp[u];
    }
    dp[u]--; 
    bridge[u] = (dp[u]==0&&u!=1), saida[u] = ++t;
}
 
string ans;
vector<ii>edges;
 
void dfs2(int u,int p,int cur){
    vis[u] = 1;
    for(auto [v,idx]:g[u]){
        if(vis[v])continue;
        dfs2(v,u,idx);
        ckmin(ranges[u][0].first, ranges[v][0].first),ckmin(ranges[u][1].first, ranges[v][1].first);
        ckmax(ranges[u][0].second, ranges[v][0].second),ckmax(ranges[u][1].second, ranges[v][1].second);
    }
    if(bridge[u]){
        bool ok = 0;
        if(ranges[u][0]!=make_pair(entrada[u],saida[u])){//u->p
            ans[cur] = (edges[cur].first==u?'R':'L'), ok = 1;
        }
        if(ranges[u][1]!=make_pair(entrada[u],saida[u])){//u<-p
            assert(ok==0);//impossivel os 2 acontecerem juntos
            ans[cur] = (edges[cur].first==u?'L':'R');
        }
    }
}
 
int main(){_
    int n,m,p;cin>>n>>m;
 
    ans.resize(m, 'B');
 
    for(int i=0;i<m;++i){
        int u,v;cin>>u>>v;
        edges.pb({u,v});
        if(u==v)continue;//self loops are allowed!
        g[u].pb({v,i}), g[v].pb({u,i});
    }
    for(int i=1;i<=n;++i){
        if(!lvl[i])dfs(i,i);
    }
 
    for(int i=1;i<=n;++i) ranges[i][1] = ranges[i][0] = {entrada[i], saida[i]};
 
    cin>>p;
 
    vector<ii>pairs(p);
 
    for(auto& [x,y]:pairs){
        cin>>x>>y;
        ckmin(ranges[x][0].first, entrada[y]), ckmax(ranges[x][0].second, entrada[y]);
        ckmin(ranges[y][1].first, entrada[x]), ckmax(ranges[y][1].second, entrada[x]);
    }

    for(int i=1;i<=n;++i){
        if(!vis[i])dfs2(i,i,0);
    }
    
    cout<<ans<<endl;
 
}   

• Subtask 1: 30 / 30
• Subtask 2: 30 / 30
• Subtask 3: 40 / 40