Submission #821088

#	Time	Username	Problem	Language	Result	Execution time	Memory
821088		arush_agu	One-Way Streets (CEOI17_oneway)	C++17	0 / 100	1 ms	468 KiB

oneway

#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#ifdef DEBUG
#include <time.h>
#endif

#define all(a) (a).begin(), (a).end()
#define rev(a) (a).rbegin(), (a).rend()
#define F first
#define S second
int recur_depth = 0;
#ifdef DEBUG
#define dbg(x)                                                                 \
  {                                                                            \
    ++recur_depth;                                                             \
    auto x_ = x;                                                               \
    --recur_depth;                                                             \
    cerr << string(recur_depth, '\t') << "\e[91m" << __func__ << ":"           \
         << __LINE__ << "\t" << #x << " = " << x_ << "\e[39m" << endl;         \
  }
#else
#define dbg(x)
#endif

using namespace std;
using namespace __gnu_pbds;

typedef pair<int, int> ii;

typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> llll;

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<pair<int, int>> vii;
typedef vector<vii> vvii;

typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<pair<ll, ll>> vll;
typedef vector<vll> vvll;

typedef vector<bool> vb;

template <class type1>
using ordered_set = tree<type1, null_type, less<type1>, rb_tree_tag,
                         tree_order_statistics_node_update>;

template <typename A, typename B>
ostream &operator<<(ostream &os, const pair<A, B> &p) {
  return os << '(' << p.first << ", " << p.second << ')';
}
template <typename T_container, typename T = typename enable_if<
                                    !is_same<T_container, string>::value,
                                    typename T_container::value_type>::type>
ostream &operator<<(ostream &os, const T_container &v) {
  os << '{';
  string sep;
  for (const T &x : v)
    os << sep << x, sep = ", ";
  return os << '}';
}

const ll MOD = 1e9 + 7;
// const ll MOD = 998244353;
const ll INF = 1e9;
const ld EPS = 1e-9;

struct DSU {
  int n;
  vi par, sz;
  int no_cc;

  DSU(int n) : n(n), no_cc(n), par(vi(n, -1)), sz(vi(n, 1)) {}

  int find(int u) {
    if (par[u] == -1)
      return u;
    return par[u] = find(par[u]);
  }

  void merge(int u, int v) {
    u = find(u), v = find(v);
    if (u == v)
      return;

    if (sz[u] < sz[v])
      swap(u, v);
    par[v] = u;
    sz[u] += sz[v];
    no_cc--;
  }
};

struct ST {
  int n;
  vvii st;
  vi lg2;

  const int MAXLG = 22;

  ST(int n, vii a) : n(n) {
    st = vvii(MAXLG, vii(n));
    st[0] = a;
    for (int j = 1; j < MAXLG; j++)
      for (int i = 0; i + (1 << j) <= n; i++)
        st[j][i] = min(st[j - 1][i], st[j - 1][i + (1 << (j - 1))]);

    lg2 = vi(n + 10);
    lg2[1] = 0;
    for (int i = 2; i < lg2.size(); i++)
      lg2[i] = lg2[i / 2] + 1;
  }

  int query(int l, int r) {
    if (l > r)
      swap(r, l);
    int k = lg2[r - l + 1];
    return min(st[k][l], st[k][r - (1 << k) + 1]).second;
  }
};

void solve() {
  struct Ed {
    int u, v, idx;
    bool is_bridge;
    int res;
  };

  int n, m;
  cin >> n >> m;
  vvii adj(n);
  vector<Ed> eds;
  for (int i = 0; i < m; i++) {
    int u, v;
    cin >> u >> v;
    u--, v--;
    adj[u].push_back({v, i});
    if (u != v)
      adj[v].push_back({u, i});
    eds.push_back(Ed{u, v, i, 0, 2});
  }

  int p;
  cin >> p;
  vii imp(p);
  for (auto &[x, y] : imp)
    cin >> x >> y, x--, y--;

  int timer = 0;
  vb vis(n);
  vi tin(n, -1), low(n, -1);
  function<void(int, int)> f = [&](int u, int u_par_ed_id) {
    vis[u] = 1;
    tin[u] = low[u] = timer++;
    for (auto [v, i] : adj[u])
      if (i != u_par_ed_id) {
        if (vis[v])
          low[u] = min(low[u], low[v]);
        else {
          f(v, i);
          low[u] = min(low[u], low[v]);
          if (low[v] > tin[u])
            eds[i].is_bridge = 1;
        }
      }
  };
  for (int i = 0; i < n; i++)
    if (!vis[i])
      f(i, -1);

  DSU d(n);
  for (auto &ed : eds)
    if (!ed.is_bridge) {
      d.merge(ed.u, ed.v);
    }
  vvii tree(n);
  for (auto &ed : eds)
    if (ed.is_bridge) {
      tree[d.find(ed.u)].push_back({d.find(ed.v), ed.idx});
      tree[d.find(ed.v)].push_back({d.find(ed.u), ed.idx});
    }

  int root = d.find(0);
  vii par_tree(n, {-2, -2});
  vi cnt_child(n, -1);
  vi depth(n, -1);
  vii euler;
  vi first_occ(n, -1);
  function<void(int, int)> g = [&](int u, int p) {
    if (p == -1)
      par_tree[u] = {-1, -1}, depth[u] = 0;
    cnt_child[u] = 0;
    first_occ[u] = euler.size();
    euler.push_back({depth[u], u});

    for (auto [v, i] : tree[u])
      if (v != p) {
        par_tree[v] = {u, i};
        depth[v] = depth[u] + 1;
        cnt_child[u]++;
        g(v, u);
        euler.push_back({depth[u], u});
      }
  };
  g(root, -1);

  for (auto [_, i] : euler)
    assert(d.par[i] == -1);
  assert(euler.size() == 2 * d.no_cc - 1);

  ST st(euler.size(), euler);

  vii cnt_imp(n);
  for (auto [x, y] : imp) {
    x = d.find(x), y = d.find(y);
    if (x == y)
      continue;

    int lca = st.query(first_occ[x], first_occ[y]);
    cnt_imp[x].first++, cnt_imp[y].second++;
    cnt_imp[lca].first--, cnt_imp[lca].second--;
  }

  queue<int> q;
  for (int i = 0; i < n; i++)
    if (cnt_child[i] == 0)
      q.push(i);
  while (!q.empty()) {
    int u = q.front();
    q.pop();

    auto [p, pe_id] = par_tree[u];
    if (p < 0)
      continue;

    assert(cnt_imp[u].first == 0 || cnt_imp[u].second == 0);
    if (cnt_imp[u].first > 0) {
      if (eds[pe_id].u == u)
        eds[pe_id].res = 0;
      else
        eds[pe_id].res = 1;
    }
    if (cnt_imp[u].second > 0) {
      if (eds[pe_id].u == u)
        eds[pe_id].res = 1;
      else
        eds[pe_id].res = 0;
    }

    cnt_imp[p].first += cnt_imp[u].first;
    cnt_imp[p].second += cnt_imp[u].second;

    if (--cnt_child[p] == 0)
      q.push(p);
  }

  for (int i = 0; i < m; i++) {
    if (eds[i].res == 2)
      cout << "B";
    if (eds[i].res == 0)
      cout << "R";
    if (eds[i].res == 1)
      cout << "L";
  }
  cout << "\n";
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);

  clock_t start = clock();

  int test_cases = 1;
  // cin >> test_cases;

  while (test_cases--)
    solve();

#ifdef DEBUG
  cerr << fixed << setprecision(10)
       << "\nTime Taken: " << (double)(clock() - start) / CLOCKS_PER_SEC
       << "s\n";
#endif
  return 0;
}

Compilation message (stderr)

oneway.cpp: In constructor 'DSU::DSU(int)':
oneway.cpp:95:7: warning: 'DSU::no_cc' will be initialized after [-Wreorder]
   95 |   int no_cc;
      |       ^~~~~
oneway.cpp:94:6: warning:   'vi DSU::par' [-Wreorder]
   94 |   vi par, sz;
      |      ^~~
oneway.cpp:97:3: warning:   when initialized here [-Wreorder]
   97 |   DSU(int n) : n(n), no_cc(n), par(vi(n, -1)), sz(vi(n, 1)) {}
      |   ^~~
oneway.cpp: In constructor 'ST::ST(int, vii)':
oneway.cpp:134:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  134 |     for (int i = 2; i < lg2.size(); i++)
      |                     ~~^~~~~~~~~~~~
In file included from /usr/include/c++/10/ext/pb_ds/detail/pat_trie_/pat_trie_.hpp:45,
                 from /usr/include/c++/10/ext/pb_ds/detail/container_base_dispatch.hpp:90,
                 from /usr/include/c++/10/ext/pb_ds/assoc_container.hpp:48,
                 from oneway.cpp:6:
oneway.cpp: In function 'void solve()':
oneway.cpp:233:23: warning: comparison of integer expressions of different signedness: 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
  233 |   assert(euler.size() == 2 * d.no_cc - 1);
      |          ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
oneway.cpp: In function 'int main()':
oneway.cpp:296:11: warning: unused variable 'start' [-Wunused-variable]
  296 |   clock_t start = clock();
      |           ^~~~~

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