Submission #1284124

#	Time	Username	Problem	Language	Result	Execution time	Memory
1284124		quan606303	One-Way Streets (CEOI17_oneway)	C++20	0 / 100	1 ms	332 KiB

oneway

/*
 * @Author: RMQuan 
 * @Date: 2025-10-27 22:45:01 
 * @Last Modified by: RMQuan
 * @Last Modified time: 2025-10-28 01:53:03
 */
/*idea : 



*/
#include <bits/stdc++.h>
bool M1;
#define int long long
#define ll long long
#define INTMAX INT_MAX
#define INTMIN INT_MIN
#define LONGMAX LLONG_MAX
#define LONGMIN LLONG_MIN
#define fi first
#define se second
#define memfull(a,b) memset(a,b,sizeof(a));
#define endl '\n'
#define TASK "TEST"
#define file() if (fopen(TASK".inp","r")){freopen(TASK".inp","r",stdin); freopen(TASK".out","w",stdout);}
using namespace std;
const int MOD=1e9+7;
const int maxn=1e5+7;
const int LOG=17;
vector<pair<int,int> > adj[maxn];
vector<pair<int,int> > g[maxn];
bool is_bridge[maxn];
int n,m,q,low[maxn],num[maxn],id_dfs=0;
pair<int,int> edge[maxn];
int scc_id[maxn],scc=0;
bool vst[maxn];
int up[maxn][LOG+1],h[maxn],ans[maxn];
void dfs(int u,int p)
{
    low[u]=num[u]=++id_dfs;
    for (auto v:adj[u])
    {
        if (v.se==p)continue;
        if (num[v.fi])low[u]=min(low[u],num[v.fi]);
        else
        {
            dfs(v.fi,v.se);
            low[u]=min(low[u],low[v.fi]);
            if (low[v.fi]==num[v.fi])is_bridge[v.se]=true;
        }
    }
}
void dfs_scc(int u)
{
    scc_id[u]=scc;
    for (auto v:adj[u])
    {
        if (scc_id[v.fi]||is_bridge[v.se])continue;
        dfs_scc(v.fi);
    }
}
int dp1[maxn],dp2[maxn];
void pre_dfs(int u,int p)
{
    for (auto v:g[u])
    {
        if (v.fi==p)continue;
        h[v.fi]=h[u]+1;
        up[v.fi][0]=u;
        for (int i=1;i<=LOG;i++)up[v.fi][i]=up[up[v.fi][i-1]][i-1];
        pre_dfs(v.fi,u);
    }
}
int lca(int u,int v)
{
    if (h[u]<h[v])swap(u,v);
    for (int i=LOG;i>=0;i--)if (h[up[u][i]]>=h[v])u=up[u][i];
    if (u==v)return u;
    for (int i=LOG;i>=0;i--)
    {
        if (up[u][i]!=up[v][i])
        {
            u=up[u][i];
            v=up[v][i];
        }
    }
    return up[u][0];
}
void dfs_cal(int u,int p)
{
    for (auto v:g[u])
    {
        if (v.fi==p)continue;
        dfs_cal(v.fi,u);
        if (dp1[v.fi])ans[v.fi]=1;
        else if (dp2[v.fi])ans[v.fi]=2;
        dp1[u]+=dp1[v.fi];
        dp2[u]+=dp2[v.fi];
    }
}
int32_t main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    file();
    cin>>n>>m;
    for (int i=1;i<=m;i++)
    {
        int u,v;
        cin>>u>>v;
        adj[u].push_back({v,i});
        adj[v].push_back({u,i});
        edge[i]={u,v};
    }
    for (int i=1;i<=n;i++)if(!num[i])dfs(i,0);
    for (int i=1;i<=n;i++)
    {
        if (!scc_id[i])
        {
            ++scc;
            dfs_scc(i);
        }
    }
    for (int i=1;i<=m;i++)
    {
        int u=scc_id[edge[i].fi];
        int v=scc_id[edge[i].se];
        if (u!=v)
        {
            g[u].push_back({v,i});
            g[v].push_back({u,i});
        }
    }
    h[0]=-1;
    pre_dfs(1,0);
    cin>>q;
    while (q--)
    {
        int u,v;
        cin>>u>>v;
        u=scc_id[u],v=scc_id[v];
        if (u!=v)
        {
            int LCA=lca(u,v);
            dp1[u]++;
            dp1[LCA]--;
            dp2[v]++;
            dp2[LCA]--;
        }
    }
    dfs_cal(1,0);
    for (int i=1;i<=m;i++)
    {
        int u,v;
        tie(u,v)=edge[i];
        u=scc_id[u];
        v=scc_id[v];
        if (u==v)cout<<"B";
        else
        {
            if (h[u]<h[v])
            {
                if (dp1[v])cout<<"L";
                else if (dp2[v])cout<<"R";
                else cout<<"B";
            }
            else if (h[v]<h[u])
            {
                if (dp1[u])cout<<"R";
                else if (dp2[u])cout<<"L";
                else cout<<"B";
            }
        }
    }
    bool M2;
    cerr<<"-------------------------------------------------"<<endl;
    cerr<<"Time : "<<clock()<<" ms"<<endl;
    cerr<<"Memory : "<<abs(&M2-&M1)/1024/1024<<" MB"<<endl;
    cerr<<"-------------------------------------------------"<<endl;
    return 0;
}

Compilation message (stderr)

oneway.cpp: In function 'int32_t main()':
oneway.cpp:25:50: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   25 | #define file() if (fopen(TASK".inp","r")){freopen(TASK".inp","r",stdin); freopen(TASK".out","w",stdout);}
      |                                           ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
oneway.cpp:106:5: note: in expansion of macro 'file'
  106 |     file();
      |     ^~~~
oneway.cpp:25:81: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   25 | #define file() if (fopen(TASK".inp","r")){freopen(TASK".inp","r",stdin); freopen(TASK".out","w",stdout);}
      |                                                                          ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
oneway.cpp:106:5: note: in expansion of macro 'file'
  106 |     file();
      |     ^~~~

• Subtask 1: 0 / 30
• Subtask 2: 0 / 30
• Subtask 3: 0 / 40