Submission #1027518

#	Time	Username	Problem	Language	Result	Execution time	Memory
1027518		vjudge1	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	559 ms	116808 KiB

oneway

#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
#define int long long
// #define double long double
 
#define endl '\n'
#define fastIO ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
#define setmin(x, y) x = min((x), (y))
#define setmax(x, y) x = max((x), (y))
#define sqr(x) ((x) * (x))
#define fi first
#define se second
 
// mt19937 hdp(chrono::high_resolution_clock::now().time_since_epoch().count());
// int rand(int l, int r){return l + ((hdp() % (r - l + 1)) + r - l + 1) % (r - l + 1);}
 
const int NM = 1e6 + 5;
const int mod = 1e6 + 3;
const int inf = 1e9 + 1;

vector<int> g[NM];
vector<pair<int, pair<int, int>>> G[NM];
int n, m, N, tin[NM], low[NM], timer, comp[NM];
pair<int, int> e[NM];
map<pair<int, int>, bool> is_cau, ditme, deophaicau;
map<pair<int, int>, int> val;

void dfs(int u, int p)
{
    tin[u] = low[u] = ++timer;
    for (int v : g[u]) 
        if (v != p)
        {
            if (tin[v])
                setmin(low[u], low[v]);
            else
            {
                dfs(v, u);
                if (low[v] > tin[u] && !deophaicau[{u, v}])
                    is_cau[{u, v}] = 1;
                setmin(low[u], low[v]);
            }
        }
}

bool vis[NM];

void cpr(int u)
{
    comp[u] = N;
    for (auto v : g[u]) 
    {
        if (is_cau[{u, v}] || is_cau[{v, u}])
        {
            if (comp[v])
            {
                G[N].push_back({comp[v], {u, v}});
                G[comp[v]].push_back({N, {v, u}});
            }
            continue;
        }
        if (comp[v])
            continue;
        cpr(v);
    }
}

void prep()
{
    for (int i = 1; i <= n; i++)
        if (!tin[i])
            dfs(i, 0);
    for (int i = 1; i <= n; i++)
        if (!comp[i])
        {
            ++N;
            cpr(i);
        }
}

int dp[NM], cur;

void DFS(int u)
{
    vis[u] = 1;
    for (auto v : G[u])
        if (!vis[v.fi])
        {
            DFS(v.fi);
            val[v.se] = dp[v.fi];
            dp[u] += dp[v.fi];
        }
}

pair<int, int> rev(pair<int, int> x)
{
    return {x.se, x.fi};
}

signed main()
{
    if (fopen("in.txt", "r")) {
        freopen("in.txt","r",stdin);
        freopen("out.txt","w",stdout);
    }
    fastIO
    cin >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        int u, v;
        cin >> u >> v;
        e[i] = {u, v};
        if (ditme[{u, v}] || ditme[{v, u}])
        {
            deophaicau[{u, v}] = deophaicau[{v, u}] = true;
            continue;
        }
        ditme[{u, v}] = true;
        ditme[{v, u}] = true;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    prep();
    int q;
    cin >> q;
    while (q--)
    {
        int u, v;
        cin >> u >> v;
        dp[comp[u]]++;
        dp[comp[v]]--;
    }
    for (int i = 1; i <= N; i++)
        if (!vis[i])
            DFS(i);
    for (int i = 1; i <= m; i++)
    {
        if (!val[e[i]] && !val[rev(e[i])])
            cout << 'B';
        else if (val[e[i]] < 0 || val[rev(e[i])] > 0)
            cout << 'R';
        else
            cout << 'L';
    }
}

Compilation message (stderr)

oneway.cpp: In function 'int main()':
oneway.cpp:105:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  105 |         freopen("in.txt","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~
oneway.cpp:106:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  106 |         freopen("out.txt","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

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