Submission #535455

#	Time	Username	Problem	Language	Result	Execution time	Memory
535455		chenwz	Regions (IOI09_regions)	C++11	100 / 100	2273 ms	46736 KiB

regions

// IOI2009 – Regions
#include <bits/stdc++.h>
using namespace std;
using VI = vector<int>;
using IP = pair<int, int>;
using LL = long long;
struct Emp {     // Employee
  int tin, reg;  // tin(dfs时间戳), reg(区域)
  VI ch;         // 被指导的
};
struct Reg {
  VI ids;             // 其中的Employee
  vector<IP> ranges;  // 时间戳排序的 {ID: cnt} cnt是到祖先的同reg数量
  int cnt;
};
vector<Emp> ES;
vector<Reg> RS;
void dfs(int u, int &timer) {
  auto &r = RS[ES[u].reg];
  r.ids.push_back(timer++), r.ranges.push_back({timer, ++r.cnt});
  for (int v : ES[u].ch) dfs(v, timer);
  r.ranges.push_back({timer, --r.cnt});  // 子树u终点，cnt离开子树后祖先的r数量
}
LL query_by_id(const Reg &r1, const Reg &r2) {
  LL ans = 0;  // 针对r2中的每个id，找寻r1中包含id的区间 O(|R2|log|R1|)
  auto &rv = r1.ranges;
  for (int u : r2.ids) {  // 找到第一个起点在u之后的区间，它之前的区间就是目标
    auto it = lower_bound(begin(rv), end(rv), make_pair(u, INT_MAX));
    if (it != rv.begin()) ans += prev(it)->second;
  }
  return ans;
}
LL query_by_range(const Reg &r1, const Reg &r2) {
  LL ans = 0;  // 针对r1中的每个区间，看看r2中有多少个id在其中, O(|R1|log(|R2|))
  const auto &rv = r2.ids;
  for (size_t i = 0; i + 1 < r1.ranges.size(); i++) {
    int p1 = r1.ranges[i].first, p2 = r1.ranges[i + 1].first;
    auto it1 = lower_bound(begin(rv), end(rv), p1),
         it2 = lower_bound(begin(rv), end(rv), p2);
    ans += r1.ranges[i].second * (it2 - it1);
  }
  return ans;
}
LL query_stitch(const Reg &r1, const Reg &r2) {
  LL ans = 0;  // 针对r2中的每个id，线性在r1中查找，时间O(|R1|+|R2|)
  auto p = r2.ids.begin();
  if (r1.ranges.empty()) return ans;
  while (p != r2.ids.end() && *p < r1.ranges[0].first) p++;
  for (size_t i = 0; i + 1 < r1.ranges.size() && p != r2.ids.end(); i++) {
    auto np = p;
    while (np != r2.ids.end() && *np < r1.ranges[i + 1].first) np++;
    ans += r1.ranges[i].second * (np - p), p = np;
  }
  return ans;
}
LL solve(int r1, int r2) {
  static map<IP, LL> cache;
  IP key(r1, r2);
  if (cache.count(key)) return cache[key];
  const Reg &reg1 = RS[r1], &reg2 = RS[r2];
  int sz1 = reg1.ids.size(), sz2 = reg2.ids.size();
  int costs[3] = {sz1 * ((int)log2(sz2) + 2) * 5,
                  sz2 * ((int)log2(sz1) + 2) * 5, sz1 + sz2};
  int k = min_element(costs, costs + 3) - costs;
  if (k == 0) return cache[key] = query_by_range(reg1, reg2);
  if (k == 1) return cache[key] = query_by_id(reg1, reg2);
  return cache[key] = query_stitch(reg1, reg2);
}
int main() {
  ios::sync_with_stdio(false), cin.tie(0);
  int N, R, Q, timer = 0;
  cin >> N >> R >> Q, ES.resize(N), RS.resize(R);
  cin >> ES[0].reg, --ES[0].reg;
  for (int i = 1, fa; i < N; i++)
    cin >> fa >> ES[i].reg, --ES[i].reg, ES[fa - 1].ch.push_back(i);
  dfs(0, timer);
  // for (int i = 0; i < R; i++) {
  //   if (RS[i].ids.empty()) continue;
  //   printf("reg %d: ", i + 1);
  //   for (int id : RS[i].ids) printf(" %d, ", id + 1);
  //   puts("");
  //   for (auto p : RS[i].ranges) {
  //     printf("%d(%d),  ", p.first, p.second);
  //   }
  //   puts("");
  // }
  for (int q = 0, r1, r2; q < Q; q++) {
    cin >> r1 >> r2;
    // printf("query : %d-%d\n", r1, r2);
    cout << solve(r1 - 1, r2 - 1) << endl;
  }
  return 0;
}

• Subtask 1: 15 / 15
• Subtask 2: 85 / 85