Submission #1094135

#	Time	Username	Problem	Language	Result	Execution time	Memory
1094135		Wjsc	Joker (BOI20_joker)	C++14	41 / 100	1010 ms	23636 KiB

Joker

#include<bits/stdc++.h>

using namespace std;

#define pi pair<int, int>
#define fi first
#define se second
#define all(v) v.begin(), v.end()

const int N = 2e5 + 5;

using tp = tuple<int, int, int>;

int n, m, q;
pi edge[N];
tp Q[N];
vector<int> ad[N];

namespace sub2 {
  bool ok = 0;
  int col[N];

  void dfs(int u, int c) {
    col[u] = c;
    for(auto v : ad[u]) {
      if(col[v] == col[u]) {
        ok = 1;
        return;
      }
      if(col[v] == -1) dfs(v, c ^ 1);
    }
  }

  void solve() {
    while(q--) {
      int l, r; cin >> l >> r;

      for(int i = 1; i <= n; ++i) ad[i].clear();

      for(int i = 1; i < l; ++i) {
        int u, v; tie(u, v) = edge[i];
        ad[u].push_back(v);
        ad[v].push_back(u);
      }
      for(int i = r + 1; i <= m; ++i) {
        int u, v; tie(u, v) = edge[i];
        ad[u].push_back(v);
        ad[v].push_back(u);
      }

      for(int i = 1; i <= n; ++i) col[i] = -1;

      ok = 0;
      for(int i = 1; i <= n; ++i)
        if(col[i] == -1) {
          dfs(i, 0);
          if(ok) break;
        }

      cout << (ok ? "YES\n" : "NO\n");
    }
  }
}

///
namespace sub3 {
  int par[N], sz[N], lz[N], ans[N];
  vector<int> L;
  vector<pi> queries[N];

  void make_set() {
    for(int i = 1; i <= n; ++i) par[i] = i, sz[i] = 1, lz[i] = 0;
  }

  int find_set(int v, int &c) {
    c ^= lz[v];
    if(v == par[v]) return v;
    return find_set(par[v], c);
  }

  void union_set(int a, int b) {
    int ca = 0, cb = 0;
    a = find_set(a, ca); b = find_set(b, cb);
    if(a != b) {
      if(sz[a] < sz[b]) swap(a, b);
      sz[a] += sz[b];
      par[b] = a;
      if(ca == cb) lz[b] = 1;
    }
  }

  bool check(int a, int b) {
    int ca = 0, cb = 0;
    a = find_set(a, ca); b = find_set(b, cb);
    if(a == b && ca == cb) return true;
    return false;
  }

  void solve() {
    sort(Q + 1, Q + q + 1);

    for(int i = 1, cur = 0; i <= q; ++i) {
      int l, r, id; tie(l, r, id) = Q[i];
      if(l != cur) cur = l, L.push_back(cur);
      queries[cur].emplace_back(r, id);
    }

    for(auto x : L) sort(all(queries[x]), greater<pi>());

    for(auto l : L) {
      make_set();
      bool ok = 0;

      for(int i = 1; i < l; ++i) {
        int u, v; tie(u, v) = edge[i];
        if(check(u, v)) ok = 1;
        union_set(u, v);
      }

      int j = m;
      for(int i = m; i > queries[l][0].fi; --i) {
        int u, v; tie(u, v) = edge[i];
        if(check(u, v)) ok = 1;
        union_set(u, v);
        j = i;
      }
      ans[queries[l][0].se] = ok;

      for(int i = 1; i < queries[l].size(); ++i) {
        int r, id; tie(r, id) = queries[l][i];
        if(ok) {
          ans[id] = ok;
          continue;
        }

        while(j > r) {
          if(check(edge[j].fi, edge[j].se)) ok = 1;
          union_set(edge[j].fi, edge[j].se);
          --j;
        }
        ans[id] = ok;
      }
    }

    for(int i = 1; i <= q; ++i) cout << (ans[i] ? "YES\n" : "NO\n");
  }
}

signed main() {
  cin.tie(0)->sync_with_stdio(0);

  if(fopen("task.inp", "r")) {
    freopen("task.inp", "r", stdin);
    freopen("task.out", "w", stdout);
  }

  cin >> n >> m >> q;

  for(int i = 1; i <= m; ++i) {
    int u, v; cin >> u >> v;
    edge[i] = {u, v};
  }

  bool chk = 1;
  for(int i = 1; i <= q; ++i) {
    int l, r; cin >> l >> r;
    Q[i] = {l, r, i};
    if(l > 200) chk = 0;
  }

  if(chk) sub3 :: solve();
  else if(n <= 2000 && m <= 2000 && q <= 2000) sub2 :: solve();
}

Compilation message (stderr)

Joker.cpp: In function 'void sub3::solve()':
Joker.cpp:129:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  129 |       for(int i = 1; i < queries[l].size(); ++i) {
      |                      ~~^~~~~~~~~~~~~~~~~~~
Joker.cpp: In function 'int main()':
Joker.cpp:153:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  153 |     freopen("task.inp", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Joker.cpp:154:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  154 |     freopen("task.out", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 6 / 6
• Subtask 2: 0 / 8
• Subtask 3: 25 / 25
• Subtask 4: 10 / 10
• Subtask 5: 0 / 22
• Subtask 6: 0 / 29