Submission #1073088

#	Time	Username	Problem	Language	Result	Execution time	Memory
1073088		cadmiumsky	The Ties That Guide Us (CEOI23_incursion)	C++17	60 / 100	281 ms	15124 KiB

incursion

#include <vector>
#include "incursion.h"
#include <cstdio>

#include <bits/stdc++.h>
#define all(x) (x).begin(),(x).end()
using namespace std;

#define sz(x) ((int)(x).size())

using pii = pair<int, int>;
using tii = tuple<int, int, int>;



const int nmax = 45e3 + 5;

vector<int> g[nmax];

int area[nmax];
int father[nmax];
#define N uhasfuhafs
int N;

void initarea(int node, int f) {
   area[node] = 1;
   father[node] = f;
   for(auto x : g[node]) {
      if(x == f) continue;
      initarea(x, node);
      area[node] += area[x];
   }
   return;
}
pii findcentr(int node, int f) {
   for(auto x : g[node]) {
      if(x == f) continue;
      if(area[x] * 2 == N) { return pii{node, x}; }
      if(area[x] * 2 > N) { return findcentr(x, node); }
   }
   return pii{node, node};
}

int make_graph(vector<pii> F) {
   for(auto &[a, b] : F) --a, --b;
   N = sz(F) + 1;
   for(int i = 0; i <= N + 1; i++) g[i].clear();
   
   for(auto [a, b] : F) {
      g[a].emplace_back(b);
      g[b].emplace_back(a);
   }
   
   int cnt = 0;
   for(int i = 0; i < N; i++) {
      if(sz(g[i]) == 2) cnt++;
   }
   if(cnt == 1) {      
      for(int i = 0; i < N; i++)
         if(sz(g[i]) == 2) return i;
   }
   
   initarea(0, 0);
   auto [u_, v_] = findcentr(0, 0);
   int root;
   
   if(u_ != v_) {
      for(int i = 0; i < sz(g[u_]); i++) {
         if(g[u_][i] == v_) {
            swap(g[u_][i], g[u_].back());
            g[u_].pop_back();
            break;
         }
      }
      for(int i = 0; i < sz(g[v_]); i++) {
         if(g[v_][i] == u_) {
            swap(g[v_][i], g[v_].back());
            g[v_].pop_back();
            break;
         }
      }
      g[u_].emplace_back(N);
      g[v_].emplace_back(N);
      g[N].emplace_back(u_);
      g[N].emplace_back(v_);
      N++;
      root = N - 1;
   }
   else { root = u_; }
   
   initarea(root, root);
   for(auto x : g[root])
      assert(area[x] * 2 < N);
   
   return root;
}

vector<int> known;

bool dfs(int node, int f, int where) {
   bool znayu = node == where;
   for(auto x : g[node]) {
      if(x == f) continue;
      znayu |= dfs(x, node, where);
   }
   known[node] = znayu;
   return known[node];
}

std::vector<int> mark(std::vector<std::pair<int, int>> F, int safe) {
   --safe;
   int root = make_graph(F);
   known.resize(N);
   dfs(root, root, safe);
   //cerr << root + 1 << '\n';
   known.resize(sz(F) + 1);
   return known;
}

int go(int x) {
   return visit(x +1);
}

void locate(std::vector<std::pair<int, int>> F, int curr, int t) {
   --curr;
   int root = make_graph(F);
   //for(int i = 0; i< N; i++) {
      //cerr << i << ": ";
      //for(auto x : g[i]) cerr << x << ' ';
      //cerr << '\n';
   //}
   known.assign(N, -1);
   if(N != sz(F) + 1)
      known.back() = 1;
   initarea(root, root);
   
   while(1) {
      if(t == 0) {
         int u = father[curr];
         if(u == sz(F) + 1) {
            curr = g[u][0] ^ g[u][1] ^ curr;
            t = go(curr);
         }
         else {
            curr = father[curr];
            t = go(curr);
         }
      }
      else {
         int a = -1, b = -1;
         for(auto x : g[curr]) {
            if(x == father[curr]) continue;
            if(a == -1) a = x;
            else b = x;
         }
         
         //cerr << curr << ": " << a << ' ' << b << '\n';
         
         if(a == -1 && b == -1) return;
         if(b == -1) {
            int h = go(a);
            if(h == 1) {
               curr = a;
               t = 1;
               continue;
            }
            go(curr);
            return;
         }
         else {
            if(area[a] < area[b]) swap(a, b);
            int h = go(a);
            if(h == 1) {
               curr = a;
               t = 1;
               continue;
            }
            go(curr);
            h = go(b);
            if(h == 1) {
               curr = b;
               t = 1;
                continue;
            }
            go(curr);
            return;
         }
      }
   }
   
}

#undef N

Compilation message (stderr)

interface.cpp: In function 'int main()':
interface.cpp:44:55: warning: comparison of integer expressions of different signedness: 'size_t' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   44 |     if(fread(T.data(), sizeof(int), 2 * N - 2, stdin) != 2 * N - 2) exit(0);
      |        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
interface.cpp:50:33: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   50 |         int l = (numbers.size() == N ? N : 0);
      |                  ~~~~~~~~~~~~~~~^~~~

• Subtask 0: 0 / 0
• Subtask 1: 30 / 30
• Subtask 2: 30 / 30
• Subtask 3: 0 / 40