Submission #900549

#	Time	Username	Problem	Language	Result	Execution time	Memory
900549		gun_gan	Dreaming (IOI13_dreaming)	C++17	18 / 100	31 ms	13788 KiB

dreaming

#include "dreaming.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

const int MX = 1e5 + 5;
int N, M, L;
vector<pair<int,int>> g[MX];

bool vis[MX];
int cur = 0, mx = 0, z = 0, len = 0;
vector<int> vec;
int p = 0, q = 0;
pair<int,int> par[MX];

void dfs(int v) {
      vis[v] = 1;
      vec.push_back(v);
      if(cur > mx) {
            mx = cur;
            z = v;
      }
      for(auto [u, w] : g[v]) {
            if(!vis[u]) {
                  if(cur + w > len / 2 && !p && len > 0) {
                        p = cur;
                        q = len - cur;
                  }
                  cur += w;
                  par[u] = {v, w};
                  dfs(u);
                  cur -= w;
            }
      }
}

vector<pair<int,int>> P;

int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
      for(int i = 0; i < M; i++) {
            g[A[i]].push_back({B[i], T[i]});
            g[B[i]].push_back({A[i], T[i]});
      }

      for(int i = 1; i <= N; i++) {
            if(vis[i]) continue;
            vec.clear();
            cur = 0, mx = 0, z = 0, len = 0, p = 0, q = 0;

            dfs(i);
            for(auto x : vec) {
                  vis[x] = 0;
                  par[x] = {z, 0};
            }

            if(vec.size() == 1) {
                  for(auto x : vec) {
                        vis[x] = 1;
                  }
                  P.push_back({0, 0});
                  continue;
            }

            if(vec.size() == 2) {
                  for(auto x : vec) {
                        vis[x] = 1;
                  }
                  P.push_back({mx, 0});
                  continue;
            }

            vec.clear();
            int tz = z;
            cur = 0, mx = 0, z = 0;
            dfs(tz);

            len = mx;

            int k = z, sum = 0, y = 2e9;
            while(k != tz) {
                  if(abs((sum) - (len - sum)) < y) {
                        y = abs((sum) - (len - sum));
                        p = sum;
                        q = len - sum;
                  }
                  sum += par[k].second;
                  k = par[k].first;
            }

            vec.clear();

            P.push_back({max(p, q), min(p, q)});
      }

      sort(P.rbegin(), P.rend());

      int ans = 0;

      for(auto [x, y] : P) {
            ans = max(ans, x + y);
      }

      if(P.size() > 1) {
            ans = max(ans, P[0].first + L + P[1].first);
      }

      if(P.size() > 2) {
            ans = max(ans, P[1].first + 2 * L + P[2].first);
      }

      return ans;
}

/*
int aa[100], bb[100], cc[100];

int main() {
      aa[0] = 1, bb[0] = 2, cc[0] = 2;
      aa[1] = 2, bb[1] = 3, cc[1] = 3;
      aa[2] = 4, bb[2] = 5, cc[2] = 3;
      aa[3] = 5, bb[3] = 6, cc[3] = 2;
      cout << travelTime(6, 4, 2, aa, bb, cc) << '\n';
}
*/

• Subtask 1: 0 / 14
• Subtask 2: 0 / 10
• Subtask 3: 0 / 23
• Subtask 4: 18 / 18
• Subtask 5: 0 / 12
• Subtask 6: 0 / 23