Submission #556053

#	Time	Username	Problem	Language	Result	Execution time	Memory
556053		Tien_Noob	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	132 ms	29120 KiB

oneway

//Make CSP great again
//Vengeance
#include <bits/stdc++.h>
#define TASK "TESTCODE"
#define Log2(x) 31 - __builtin_clz(x)
using namespace std;
const int N = 1e5, cbit = 16;
vector<int> adj[N + 1], edge[N + 1];
int n, m, q, l[N + 1], r[N + 1], dp[N + 1][2], f[N + 1][cbit + 1], p[N + 1], res[N + 1], depth[N + 1];
int num[N + 1], low[N + 1], Count, Comp[N + 1], CompCount;
stack<int> st;
bool visited[N + 1];
void read()
{
    cin >> n >> m;
    for (int i = 1; i <= m; ++ i)
    {
        cin >> l[i] >> r[i];
        adj[l[i]].push_back(i);
        adj[r[i]].push_back(i);
    }
}
void visit(int u, int pre)
{
    st.push(u);
    num[u] = low[u] = ++Count;
    for (int i : adj[u])
    {
        if (i == pre)
        {
            continue;
        }
        int v = l[i] ^ u ^ r[i];
        if (num[v])
        {
            low[u] = min(low[u], num[v]);
        }
        else
        {
            visit(v, i);
            low[u] = min(low[u], low[v]);
        }
    }
    if (low[u] == num[u])
    {
        int v;
        ++CompCount;
        do
        {
            v = st.top();
            st.pop();
            Comp[v] = CompCount;
            low[v] = num[v] = 1e9;
        }
        while(v != u);
    }
}
void Compress(int u)
{
    visited[u] = true;
    for (int i : adj[u])
    {
        int v = l[i] ^ r[i] ^ u;
        if (Comp[u] == Comp[v])
        {
            res[i] = 2;
        }
        if (visited[v])
        {
            continue;
        }
        if (Comp[v] != Comp[u])
        {
            p[Comp[v]] = i;
            edge[Comp[u]].push_back(Comp[v]);
            depth[Comp[v]] = depth[Comp[u]] + 1;
            f[Comp[v]][0] = Comp[u];
            for (int k = 1; k <= cbit; ++ k)
            {
                f[Comp[v]][k] = f[f[Comp[v]][k - 1]][k - 1];
            }
            //cerr << Comp[u] << ' ' << Comp[v] << '\n';
        }
        Compress(v);
    }
}
int LCA(int u, int v)
{
    if (depth[u] > depth[v])
    {
        swap(u, v);
    }
    int k = depth[v] - depth[u];
    for (int i = cbit; i >= 0; -- i)
    {
        if ((k >> i) & 1)
        {
            v = f[v][i];
        }
    }
    if (u == v)
    {
        return u;
    }
    for (int i = cbit; i >= 0; -- i)
    {
        if (f[u][i] != f[v][i])
        {
            u = f[u][i];
            v = f[v][i];
        }
    }
    return f[u][0];
}
void DFS(int u)
{
    //0 : R, 1 : L, 2 : B
    for (int v : edge[u])
    {
        DFS(v);
        dp[u][0] += dp[v][0];
        dp[u][1] += dp[v][1];
        int i = p[v];
        if (dp[v][0] == 0 && dp[v][1] == 0)
        {
            res[i] = 2;
            continue;
        }
        if (dp[v][0] > 0 && depth[Comp[l[i]]] < depth[Comp[r[i]]])
        {
            res[i] = 1;
        }
        if (dp[v][1] > 0 && depth[Comp[l[i]]] > depth[Comp[r[i]]])
        {
            res[i] = 1;
        }
    }
}
void solve()
{
    for (int i = 1; i <= n; ++ i)
    {
        if (num[i] == 0)
        {
            visit(i, 0);
        }
    }
    //cerr << Comp[1] << ' ' << Comp[2] << '\n';
    for (int i = 1; i <= n; ++ i)
    {
        if (!visited[i])
        {
            Compress(i);
        }
    }
    cin >> q;
    while(q--)
    {
        int u, v;
        cin >> u >> v;
        u = Comp[u];
        v = Comp[v];
        if (u == v)
        {
            continue;
        }
        int l = LCA(u, v);
        ++dp[u][0];
        --dp[l][0];
        ++dp[v][1];
        --dp[l][1];
        //cerr << u << ' ' << l << ' ' << v << '\n';
    }
    for (int i = 1; i <= CompCount; ++ i)
    {
        if (depth[i] == 0)
        {
            DFS(i);
        }
    }
    for (int i = 1; i <= m; ++ i)
    {
        if (res[i] == 2)
        {
            cout << 'B';
        }
        if (res[i] == 1)
        {
            cout << 'L';
        }
        if (res[i] == 0)
        {
            cout << 'R';
        }
    }
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    if (fopen(TASK".INP", "r"))
    {
        freopen(TASK".INP", "r", stdin);
        //freopen(TASK".OUT", "w", stdout);
    }
    int t = 1;
    bool typetest = false;
    if (typetest)
    {
        cin >> t;
    }
    for (int __ = 1; __ <= t; ++ __)
    {
        //cout << "Case " << __ << ": ";
        read();
        solve();
    }
}

Compilation message (stderr)

oneway.cpp: In function 'int main()':
oneway.cpp:203:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  203 |         freopen(TASK".INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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