Submission #259154

#	Time	Username	Problem	Language	Result	Execution time	Memory
259154		KoD	Beads and wires (APIO14_beads)	C++17	100 / 100	284 ms	28396 KiB

beads

#line 1 "main.cpp"

/**
 * @title Template
 */

#include <iostream>
#include <algorithm>
#include <utility>
#include <numeric>
#include <vector>
#include <array>
#include <tuple>
#include <cassert>
#include <random>

#line 2 "/Users/kodamankod/Desktop/Programming/Library/other/chmin_chmax.cpp"

template <class T, class U>
constexpr bool chmin(T &lhs, const U &rhs) {
  if (lhs > rhs) { 
    lhs = rhs; 
    return true; 
  }
  return false;
}

template <class T, class U>
constexpr bool chmax(T &lhs, const U &rhs) {
  if (lhs < rhs) { 
    lhs = rhs; 
    return true; 
  }
  return false;
}

/**
 * @title Chmin/Chmax
 */
#line 2 "/Users/kodamankod/Desktop/Programming/Library/other/range.cpp"

#line 4 "/Users/kodamankod/Desktop/Programming/Library/other/range.cpp"

class range {
public:
  class iterator {
  private:
    int64_t M_position;

  public:
    constexpr iterator(int64_t position) noexcept: M_position(position) { }
    constexpr void operator ++ () noexcept { ++M_position; }
    constexpr bool operator != (iterator other) const noexcept { return M_position != other.M_position; }
    constexpr int64_t operator * () const noexcept { return M_position; }

  };

  class reverse_iterator {
  private:
    int64_t M_position;
  
  public:
    constexpr reverse_iterator(int64_t position) noexcept: M_position(position) { }
    constexpr void operator ++ () noexcept { --M_position; }
    constexpr bool operator != (reverse_iterator other) const noexcept { return M_position != other.M_position; }
    constexpr int64_t operator * () const noexcept { return M_position; }

  };
  
private:
  const iterator M_first, M_last;

public:
  constexpr range(int64_t first, int64_t last) noexcept: M_first(first), M_last(std::max(first, last)) { }
  constexpr iterator begin() const noexcept { return M_first; }
  constexpr iterator end() const noexcept { return M_last; }
  constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(*M_last - 1); } 
  constexpr reverse_iterator rend() const noexcept { return reverse_iterator(*M_first - 1); } 

};

/**
 * @title Range
 */
#line 2 "/Users/kodamankod/Desktop/Programming/Library/other/rev.cpp"

#include <type_traits>
#include <iterator>
#line 6 "/Users/kodamankod/Desktop/Programming/Library/other/rev.cpp"

template <class T>
class rev_impl {
public:
  using iterator = typename std::decay<T>::type::reverse_iterator;

private:
  const iterator M_begin;
  const iterator M_end;

public:
  constexpr rev_impl(T &&cont) noexcept: M_begin(std::rbegin(cont)), M_end(std::rend(cont)) { }
  constexpr iterator begin() const noexcept { return M_begin; }
  constexpr iterator end() const noexcept { return M_end; }

};

template <class T>
constexpr decltype(auto) rev(T &&cont) {
  return rev_impl<T>(std::forward<T>(cont));
}

/**
 * @title Reverser
 */
#line 19 "main.cpp"

using i32 = int32_t;
using i64 = int64_t;
using u32 = uint32_t;
using u64 = uint64_t;

constexpr i32 inf32 = (i32(1) << 30) - 1;
constexpr i64 inf64 = (i64(1) << 62) - 1;

struct edge_t {
  i32 to, cost;
  edge_t(i32 t, i32 c): to(t), cost(c) { }
};

i32 N, ans;
std::vector<edge_t> graph[200000];
i32 root[200000], max_c[200000];

void dfs(i32 u, i32 p) {
  root[u] = 0;
  max_c[u] = -inf32;
  for (auto [v, c]: graph[u]) {
    if (v == p) continue;
    dfs(v, u);
    i32 tmp = std::max(root[v], root[v] + max_c[v] + c);
    root[u] += tmp;
    chmax(max_c[u], root[v] + c - tmp);
  }
}

void push(i32 u, i32 p, i32 rt, i32 mc) {
  root[u] = 0;
  max_c[u] = -inf32;
  for (auto [v, c]: graph[u]) {
    if (v == p) {
      root[v] = rt;
      max_c[v] = mc;
    }
    i32 tmp = std::max(root[v], root[v] + max_c[v] + c);
    root[u] += tmp;
    chmax(max_c[u], root[v] + c - tmp);
  }
  chmax(ans, root[u]);
  i32 size = graph[u].size();
  std::vector<i32> rt_pref(size + 1), mc_pref(size + 1, -inf32);
  {
    i32 idx = 0;
    for (auto [v, c]: graph[u]) {
      ++idx;
      i32 tmp = std::max(root[v], root[v] + max_c[v] + c);
      rt_pref[idx] = rt_pref[idx - 1] + tmp;
      mc_pref[idx] = std::max(mc_pref[idx - 1], root[v] + c - tmp);
    }
  }
  std::vector<i32> rt_suff(size + 1), mc_suff(size + 1, -inf32);
  {
    i32 idx = 0;
    for (auto [v, c]: rev(graph[u])) {
      ++idx;
      i32 tmp = std::max(root[v], root[v] + max_c[v] + c);
      rt_suff[idx] = rt_suff[idx - 1] + tmp;
      mc_suff[idx] = std::max(mc_suff[idx - 1], root[v] + c - tmp);
    }
  }
  for (auto i: range(0, size)) {
    auto [v, c] = graph[u][i];
    if (v != p) {
      push(v, u, rt_pref[i] + rt_suff[size - i - 1], std::max(mc_pref[i], mc_suff[size - i - 1]));
    }
  }
}

int main() {
  std::ios_base::sync_with_stdio(false);
  std::cin.tie(nullptr);
  std::cin >> N;
  for (i32 i = 1; i < N; ++i) {
    i32 u, v, c;
    std::cin >> u >> v >> c;
    --u; --v;
    graph[u].emplace_back(v, c);
    graph[v].emplace_back(u, c);
  }
  dfs(0, -1);
  push(0, -1, 0, -inf32);
  std::cout << ans << '\n';
  return 0;
}

Compilation message (stderr)

main.cpp: In function 'void push(i32, i32, i32, i32)':
main.cpp:84:15: warning: unused variable 'c' [-Wunused-variable]

• Subtask 1: 13 / 13
• Subtask 2: 15 / 15
• Subtask 3: 29 / 29
• Subtask 4: 43 / 43