Submission #628491

#	Time	Username	Problem	Language	Result	Execution time	Memory
628491		Benq	Thousands Islands (IOI22_islands)	C++17	100 / 100	419 ms	34396 KiB

islands

#include "islands.h"
 
#include <variant>
#include <vector>
 
#include <bits/stdc++.h>
using namespace std;
 
using ll = long long;
using db = long double; // or double, if TL is tight
using str = string; // yay python! 
 
// pairs
using pi = pair<int,int>;
using pl = pair<ll,ll>;
using pd = pair<db,db>;
#define mp make_pair
#define f first
#define s second
 
#define tcT template<class T
#define tcTU tcT, class U
// ^ lol this makes everything look weird but I'll try it
tcT> using V = vector<T>; 
tcT, size_t SZ> using AR = array<T,SZ>; 
using vi = V<int>;
using vb = V<bool>;
using vl = V<ll>;
using vd = V<db>;
using vs = V<str>;
using vpi = V<pi>;
using vpl = V<pl>;
using vpd = V<pd>;
 
// vectors
// oops size(x), rbegin(x), rend(x) need C++17
#define sz(x) int((x).size())
#define bg(x) begin(x)
#define all(x) bg(x), end(x)
#define rall(x) x.rbegin(), x.rend() 
#define sor(x) sort(all(x)) 
#define rsz resize
#define ins insert 
#define pb push_back
#define eb emplace_back
#define ft front()
#define bk back()
 
#define lb lower_bound
#define ub upper_bound
tcT> int lwb(V<T>& a, const T& b) { return int(lb(all(a),b)-bg(a)); }
tcT> int upb(V<T>& a, const T& b) { return int(ub(all(a),b)-bg(a)); }
 
// loops
#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i,a) ROF(i,0,a)
#define rep(a) F0R(_,a)
#define each(a,x) for (auto& a: x)
 
const int MOD = 1e9+7; // 998244353;
const int MX = 2e5+5;
const ll BIG = 1e18; // not too close to LLONG_MAX
const db PI = acos((db)-1);
const int dx[4]{1,0,-1,0}, dy[4]{0,1,0,-1}; // for every grid problem!!
mt19937 rng((uint32_t)chrono::steady_clock::now().time_since_epoch().count()); 
template<class T> using pqg = priority_queue<T,vector<T>,greater<T>>;
 
// bitwise ops
// also see https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html
constexpr int pct(int x) { return __builtin_popcount(x); } // # of bits set
constexpr int bits(int x) { // assert(x >= 0); // make C++11 compatible until USACO updates ...
  return x == 0 ? 0 : 31-__builtin_clz(x); } // floor(log2(x)) 
constexpr int p2(int x) { return 1<<x; }
constexpr int msk2(int x) { return p2(x)-1; }
 
ll cdiv(ll a, ll b) { return a/b+((a^b)>0&&a%b); } // divide a by b rounded up
ll fdiv(ll a, ll b) { return a/b-((a^b)<0&&a%b); } // divide a by b rounded down
 
tcT> bool ckmin(T& a, const T& b) {
  return b < a ? a = b, 1 : 0; } // set a = min(a,b)
tcT> bool ckmax(T& a, const T& b) {
  return a < b ? a = b, 1 : 0; } // set a = max(a,b)
 
tcTU> T fstTrue(T lo, T hi, U f) {
  ++hi; assert(lo <= hi); // assuming f is increasing
  while (lo < hi) { // find first index such that f is true 
    T mid = lo+(hi-lo)/2;
    f(mid) ? hi = mid : lo = mid+1; 
  } 
  return lo;
}
tcTU> T lstTrue(T lo, T hi, U f) {
  --lo; assert(lo <= hi); // assuming f is decreasing
  while (lo < hi) { // find first index such that f is true 
    T mid = lo+(hi-lo+1)/2;
    f(mid) ? lo = mid : hi = mid-1;
  } 
  return lo;
}
tcT> void remDup(vector<T>& v) { // sort and remove duplicates
  sort(all(v)); v.erase(unique(all(v)),end(v)); }
tcTU> void erase(T& t, const U& u) { // don't erase
  auto it = t.find(u); assert(it != end(t));
  t.erase(it); } // element that doesn't exist from (multi)set
 
#define tcTUU tcT, class ...U
 
inline namespace Helpers {
  //////////// is_iterable
  // https://stackoverflow.com/questions/13830158/check-if-a-variable-type-is-iterable
  // this gets used only when we can call begin() and end() on that type
  tcT, class = void> struct is_iterable : false_type {};
  tcT> struct is_iterable<T, void_t<decltype(begin(declval<T>())),
                                    decltype(end(declval<T>()))
                                   >
                         > : true_type {};
  tcT> constexpr bool is_iterable_v = is_iterable<T>::value;
 
  //////////// is_readable
  tcT, class = void> struct is_readable : false_type {};
  tcT> struct is_readable<T,
          typename std::enable_if_t<
              is_same_v<decltype(cin >> declval<T&>()), istream&>
          >
      > : true_type {};
  tcT> constexpr bool is_readable_v = is_readable<T>::value;
 
  //////////// is_printable
  // // https://nafe.es/posts/2020-02-29-is-printable/
  tcT, class = void> struct is_printable : false_type {};
  tcT> struct is_printable<T,
          typename std::enable_if_t<
              is_same_v<decltype(cout << declval<T>()), ostream&>
          >
      > : true_type {};
  tcT> constexpr bool is_printable_v = is_printable<T>::value;
}
 
inline namespace Input {
  tcT> constexpr bool needs_input_v = !is_readable_v<T> && is_iterable_v<T>;
  tcTUU> void re(T& t, U&... u);
  tcTU> void re(pair<T,U>& p); // pairs
 
  // re: read
  tcT> typename enable_if<is_readable_v<T>,void>::type re(T& x) { cin >> x; } // default
  tcT> void re(complex<T>& c) { T a,b; re(a,b); c = {a,b}; } // complex
  tcT> typename enable_if<needs_input_v<T>,void>::type re(T& i); // ex. vectors, arrays
  tcTU> void re(pair<T,U>& p) { re(p.f,p.s); }
  tcT> typename enable_if<needs_input_v<T>,void>::type re(T& i) {
    each(x,i) re(x); }
  tcTUU> void re(T& t, U&... u) { re(t); re(u...); } // read multiple
 
  // rv: resize and read vectors
  void rv(size_t) {}
  tcTUU> void rv(size_t N, V<T>& t, U&... u);
  template<class...U> void rv(size_t, size_t N2, U&... u);
  tcTUU> void rv(size_t N, V<T>& t, U&... u) {
    t.rsz(N); re(t);
    rv(N,u...); }
  template<class...U> void rv(size_t, size_t N2, U&... u) {
    rv(N2,u...); }
 
  // dumb shortcuts to read in ints
  void decrement() {} // subtract one from each
  tcTUU> void decrement(T& t, U&... u) { --t; decrement(u...); }
  #define ints(...) int __VA_ARGS__; re(__VA_ARGS__);
  #define int1(...) ints(__VA_ARGS__); decrement(__VA_ARGS__);
}
 
inline namespace ToString {
  tcT> constexpr bool needs_output_v = !is_printable_v<T> && is_iterable_v<T>;
 
  // ts: string representation to print
  tcT> typename enable_if<is_printable_v<T>,str>::type ts(T v) {
    stringstream ss; ss << fixed << setprecision(15) << v;
    return ss.str(); } // default
  tcT> str bit_vec(T t) { // bit vector to string
    str res = "{"; F0R(i,sz(t)) res += ts(t[i]);
    res += "}"; return res; }
  str ts(V<bool> v) { return bit_vec(v); }
  template<size_t SZ> str ts(bitset<SZ> b) { return bit_vec(b); } // bit vector
  tcTU> str ts(pair<T,U> p); // pairs
  tcT> typename enable_if<needs_output_v<T>,str>::type ts(T v); // vectors, arrays
  tcTU> str ts(pair<T,U> p) { return "("+ts(p.f)+", "+ts(p.s)+")"; }
  tcT> typename enable_if<is_iterable_v<T>,str>::type ts_sep(T v, str sep) {
    // convert container to string w/ separator sep
    bool fst = 1; str res = "";
    for (const auto& x: v) {
      if (!fst) res += sep;
      fst = 0; res += ts(x);
    }
    return res;
  }
  tcT> typename enable_if<needs_output_v<T>,str>::type ts(T v) {
    return "{"+ts_sep(v,", ")+"}"; }
 
  // for nested DS
  template<int, class T> typename enable_if<!needs_output_v<T>,vs>::type 
    ts_lev(const T& v) { return {ts(v)}; }
  template<int lev, class T> typename enable_if<needs_output_v<T>,vs>::type 
    ts_lev(const T& v) {
    if (lev == 0 || !sz(v)) return {ts(v)};
    vs res;
    for (const auto& t: v) {
      if (sz(res)) res.bk += ",";
      vs tmp = ts_lev<lev-1>(t);
      res.ins(end(res),all(tmp));
    }
    F0R(i,sz(res)) {
      str bef = " "; if (i == 0) bef = "{";
      res[i] = bef+res[i];
    }
    res.bk += "}";
    return res;
  }
}
 
inline namespace Output {
  template<class T> void pr_sep(ostream& os, str, const T& t) { os << ts(t); }
  template<class T, class... U> void pr_sep(ostream& os, str sep, const T& t, const U&... u) {
    pr_sep(os,sep,t); os << sep; pr_sep(os,sep,u...); }
  // print w/ no spaces
  template<class ...T> void pr(const T&... t) { pr_sep(cout,"",t...); } 
  // print w/ spaces, end with newline
  void ps() { cout << "\n"; }
  template<class ...T> void ps(const T&... t) { pr_sep(cout," ",t...); ps(); } 
  // debug to cerr
  template<class ...T> void dbg_out(const T&... t) {
    pr_sep(cerr," | ",t...); cerr << endl; }
  void loc_info(int line, str names) {
    cerr << "Line(" << line << ") -> [" << names << "]: "; }
  template<int lev, class T> void dbgl_out(const T& t) {
    cerr << "\n\n" << ts_sep(ts_lev<lev>(t),"\n") << "\n" << endl; }
  #ifdef LOCAL
    #define dbg(...) loc_info(__LINE__,#__VA_ARGS__), dbg_out(__VA_ARGS__)
    #define dbgl(lev,x) loc_info(__LINE__,#x), dbgl_out<lev>(x)
  #else // don't actually submit with this
    #define dbg(...) 0
    #define dbgl(lev,x) 0
  #endif
 
  const clock_t beg = clock();
  #define dbg_time() dbg((db)(clock()-beg)/CLOCKS_PER_SEC)
}
 
inline namespace FileIO {
  void setIn(str s)  { freopen(s.c_str(),"r",stdin); }
  void setOut(str s) { freopen(s.c_str(),"w",stdout); }
  void setIO(str s = "") {
    cin.tie(0)->sync_with_stdio(0); // unsync C / C++ I/O streams
    // cin.exceptions(cin.failbit);
    // throws exception when do smth illegal
    // ex. try to read letter into int
    if (sz(s)) setIn(s+".in"), setOut(s+".out"); // for old USACO
  }
}
 
/**
 * Description: Disjoint Set Union with path compression
   * and union by size. Add edges and test connectivity. 
   * Use for Kruskal's or Boruvka's minimum spanning tree.
 * Time: O(\alpha(N))
 * Source: CSAcademy, KACTL
 * Verification: *
 */
 
struct DSU {
  vi e; void init(int N) { e = vi(N,-1); }
  int get(int x) { return e[x] < 0 ? x : e[x] = get(e[x]); } 
  bool sameSet(int a, int b) { return get(a) == get(b); }
  int size(int x) { return -e[get(x)]; }
  bool unite(int x, int y) { // union by size
    x = get(x), y = get(y); if (x == y) return 0;
    if (e[x] > e[y]) swap(x,y);
    e[x] += e[y]; e[y] = x; return 1;
  }
};
 
/**tcT> T kruskal(int N, vector<pair<T,pi>> ed) {
  sort(all(ed));
  T ans = 0; DSU D; D.init(N); // edges that unite are in MST
  each(a,ed) if (D.unite(a.s.f,a.s.s)) ans += a.f; 
  return ans;
}*/
 
vi operator+(vi a, vi b) {
  a.ins(end(a),all(b));
  return a;
}
 
vi rev(vi a) {
  reverse(all(a));
  return a;
}
 
std::variant<bool, std::vector<int>> find_journey(
    int N, int M, std::vector<int> U, std::vector<int> V) {
  int src = 0;
  vector<map<int,int>> in(N), out(N);
  F0R(i,M) {
    out[U[i]][i] = V[i];
    in[V[i]][i] = U[i];
  }
  queue<int> q;
  F0R(x,N) if (!sz(out[x]) || !sz(in[x])) q.push(x);
  auto remove_from_graph = [&](int x) {
    for (auto y: out[x]) {
      in[y.s].erase(y.f);
      q.push(y.s);
    }
    for (auto y: in[x]) {
      out[y.s].erase(y.f);
      q.push(y.s);
    }
    out[x].clear(), in[x].clear();
  };
  vi stk;
  while (true) {
    if (sz(q)) {
      int x = q.ft; q.pop();
      if (x == src) continue;
      if (!sz(out[x])) {
        remove_from_graph(x);
      }
      continue;
    }
    if (sz(out[src]) == 0) return false;
    if (sz(out[src]) == 1) {
      stk.pb(begin(out[src])->f);
      int nsrc = begin(out[src])->s;
      remove_from_graph(src);
      src = nsrc;
      continue;
    }
    break;
  }
  // now keep only 2 outgoing edges for the source, 1 outgoing edge for every other vertex still in the graph
  vi edges;
  F0R(i,N) if (sz(out[i])) {
    edges.pb(begin(out[i])->f);
    if (i == src) {
      assert(sz(out[i]) >= 2);
      edges.pb(next(begin(out[i]))->f);
    }
  }
  F0R(i,N) out[i].clear(), in[i].clear();
  for (int e: edges) {
    out.at(U[e])[e] = V[e];
  }
  vi ans;
  int cur = src;
  multiset<int> toggled;
  auto take_edge = [&](int e) {
    if (sz(ans)) assert(ans.bk != e);
    assert(out[cur].count(e));
    int nex = out[cur].at(e);
    out[cur].erase(e);
    out[nex][e] = cur;
    if (toggled.count(e)) toggled.erase(e);
    else toggled.ins(e);
    cur = nex; ans.pb(e);
  };
  auto take_only_cand = [&]() {
    vi cand;
    for (auto [e, _]: out[cur]) if (e != ans.bk) cand.pb(e);
    assert(sz(cand) == 1); // only one possible next edge
    take_edge(cand[0]);
  };
  take_edge(begin(out[cur])->f); // everything is forced after this
  while (sz(toggled)) {
    take_only_cand();
  }
  return stk + ans + rev(stk);
}

Compilation message (stderr)

islands.cpp: In function 'void FileIO::setIn(str)':
islands.cpp:249:31: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  249 |   void setIn(str s)  { freopen(s.c_str(),"r",stdin); }
      |                        ~~~~~~~^~~~~~~~~~~~~~~~~~~~~
islands.cpp: In function 'void FileIO::setOut(str)':
islands.cpp:250:31: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  250 |   void setOut(str s) { freopen(s.c_str(),"w",stdout); }
      |                        ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 5 / 5
• Subtask 3: 21 / 21
• Subtask 4: 24 / 24
• Subtask 5: 45 / 45