Tifa's CP Library

:heavy_check_mark: path (src/code/graph/path.hpp)

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#ifndef TIFALIBS_GRAPH_PATH
#define TIFALIBS_GRAPH_PATH

#include "alist.hpp"

namespace tifa_libs::graph {

template <class G>
CEXP std::optional<vecu> path(G CR g, u32 from, u32 to) {
  vecu ret;
  bool failed = true;
  auto dfs = [&](auto &&dfs, u32 now, u32 fa) -> void {
    ret.push_back(now);
    if (now == to) return void(failed = false);
    for (auto v : g.g[now]) {
      u32 to = 0;
      if CEXP (is_alist<G>) to = v;
      else to = v.first;
      if (to == fa) continue;
      if (dfs(dfs, to, now); !failed) return;
    }
    if (!failed) return;
    ret.pop_back();
  };
  if (dfs(dfs, from, -1_u32); failed) return {};
  return ret;
}

}  // namespace tifa_libs::graph

#endif
#line 1 "src/code/graph/path.hpp"



#line 1 "src/code/graph/alist.hpp"



#line 1 "src/code/util/util.hpp"



#include <bits/stdc++.h>

#define CEXP constexpr
#define TPN typename
#define CR const&

#define cT_(...) std::conditional_t<sizeof(__VA_ARGS__) <= sizeof(size_t), __VA_ARGS__, __VA_ARGS__ CR>
#define fle_(T, i, l, r, ...) for (T i = (l), i##e = (r)__VA_OPT__(, ) __VA_ARGS__; i <= i##e; ++i)
#define flt_(T, i, l, r, ...) for (T i = (l), i##e = (r)__VA_OPT__(, ) __VA_ARGS__; i < i##e; ++i)

#ifdef ONLINE_JUDGE
#undef assert
#define assert(x) 42
#endif

using i8 = int8_t;
using i16 = int16_t;
using i32 = int32_t;
using i64 = int64_t;
using i128 = __int128_t;
using isz = ptrdiff_t;

using u8 = uint8_t;
using u16 = uint16_t;
using u32 = uint32_t;
using u64 = uint64_t;
using u128 = __uint128_t;
using usz = size_t;

using f32 = float;
using f64 = double;
using f128 = long double;

template <class T>
using ptt = std::pair<T, T>;
template <class T>
using pt3 = std::tuple<T, T, T>;
template <class T>
using pt4 = std::tuple<T, T, T, T>;

template <class E>
using itl = std::initializer_list<E>;
template <class T, usz N>
using arr = std::array<T, N>;
template <class T>
using vec = std::vector<T>;
template <class T>
using vvec = vec<vec<T>>;
template <class T>
using v3ec = vec<vvec<T>>;
template <class U, class T>
using vecp = vec<std::pair<U, T>>;
template <class U, class T>
using vvecp = vvec<std::pair<U, T>>;
template <class T>
using vecpt = vec<ptt<T>>;
template <class T>
using vvecpt = vvec<ptt<T>>;
template <class T>
using ptvec = ptt<vec<T>>;
template <class T>
using ptvvec = ptt<vvec<T>>;

template <class T, class C = std::less<T>>
using pq = std::priority_queue<T, vec<T>, C>;
template <class T>
using pqg = std::priority_queue<T, vec<T>, std::greater<T>>;

using strn = std::string;
using strnv = std::string_view;
template <class T, usz ext = std::dynamic_extent>
using spn = std::span<T const, ext>;

#define mk_(V, A, T) using V##A = V<T>;
#define mk(A, T) mk_(ptt, A, T) mk_(pt3, A, T) mk_(pt4, A, T) mk_(vec, A, T) mk_(vvec, A, T) mk_(v3ec, A, T) mk_(vecpt, A, T) mk_(vvecpt, A, T) mk_(ptvec, A, T) mk_(ptvvec, A, T) mk_(spn, A, T) mk_(itl, A, T)
mk(b, bool) mk(i, i32) mk(u, u32) mk(ii, i64) mk(uu, u64);
#undef mk
#undef mk_

using namespace std::literals;
CEXP i8 operator""_i8(unsigned long long x) { return (i8)x; }
CEXP i16 operator""_i16(unsigned long long x) { return (i16)x; }
CEXP i32 operator""_i32(unsigned long long x) { return (i32)x; }
CEXP i64 operator""_i64(unsigned long long x) { return (i64)x; }
CEXP isz operator""_iz(unsigned long long x) { return (isz)x; }

CEXP u8 operator""_u8(unsigned long long x) { return (u8)x; }
CEXP u16 operator""_u16(unsigned long long x) { return (u16)x; }
CEXP u32 operator""_u32(unsigned long long x) { return (u32)x; }
CEXP u64 operator""_u64(unsigned long long x) { return (u64)x; }
CEXP usz operator""_uz(unsigned long long x) { return (usz)x; }

inline const auto fn_0 = [](auto&&...) {};
inline const auto fn_is0 = [](auto x) { return x == 0; };

template <std::floating_point FP>
inline FP eps_v = std::sqrt(std::numeric_limits<FP>::epsilon());
template <std::floating_point FP>
CEXP void set_eps(FP v) { eps_v<FP> = v; }
using std::numbers::pi_v;

namespace tifa_libs {
using std::min, std::max, std::swap;
template <class T>
constexpr T abs(T x) { return x < 0 ? -x : x; }
}  // namespace tifa_libs


#line 5 "src/code/graph/alist.hpp"

namespace tifa_libs::graph {

template <bool with_deg = false>
struct alist {
  using weight_type = u32;
  using value_type = vvecu;
  value_type g;
  u32 cnt_arc;
  vecu deg_in, deg_out;

  //! vertex ID: [0, n)
  explicit CEXP alist(u32 n = 0) : g(n), cnt_arc(0) {
    if CEXP (with_deg) deg_in.resize(n), deg_out.resize(n);
  }

  CEXP void add_arc(u32 u, u32 v) {
    g[u].push_back(v), ++cnt_arc;
    if CEXP (with_deg) ++deg_in[v], ++deg_out[u];
  }
};
template <class G>
concept is_alist = (std::is_base_of_v<alist<true>, G> || std::is_base_of_v<alist<false>, G>);

}  // namespace tifa_libs::graph


#line 5 "src/code/graph/path.hpp"

namespace tifa_libs::graph {

template <class G>
CEXP std::optional<vecu> path(G CR g, u32 from, u32 to) {
  vecu ret;
  bool failed = true;
  auto dfs = [&](auto &&dfs, u32 now, u32 fa) -> void {
    ret.push_back(now);
    if (now == to) return void(failed = false);
    for (auto v : g.g[now]) {
      u32 to = 0;
      if CEXP (is_alist<G>) to = v;
      else to = v.first;
      if (to == fa) continue;
      if (dfs(dfs, to, now); !failed) return;
    }
    if (!failed) return;
    ret.pop_back();
  };
  if (dfs(dfs, from, -1_u32); failed) return {};
  return ret;
}

}  // namespace tifa_libs::graph


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