Submission #73877

#	Time	Username	Problem	Language	Result	Execution time	Memory
73877		funcsr	Friend (IOI14_friend)	C++17	23 / 100	16 ms	1980 KiB

friend

#include "friend.h"
#include <vector>
#include <cassert>
#include <tuple>
#include <queue>
#define rep(i, n) for (int i=0; i<(n); i++)
#define pb push_back
#define INF 1145141919
using namespace std;
typedef pair<int, int> P;
struct Dinic {
  struct Edge{ int to, cap, rev; };
  vector<Edge> G[1002];
  int level[1002];
  void add_edge(int x, int y, int cap) {
    G[x].pb((Edge) { y, cap, (int)G[y].size() });
    G[y].pb((Edge) { x, 0, (int)G[x].size()-1 });
  }
  int dfs(int x, int goal, int f) {
    if (x == goal) return f;
    for (Edge &e : G[x]) if (level[x] < level[e.to] && e.cap > 0) {
      int w = min(f, e.cap);
      int ret = dfs(e.to, goal, w);
      if (ret > 0) {
        e.cap -= w;
        G[e.to][e.rev].cap += w;
        return ret;
      }
    }
    return 0;
  }
  void bfs(int s) {
    rep(i, 1002) level[i] = INF;
    level[s] = 0;
    queue<int> q;
    q.push(s);
    while (!q.empty()) {
      int x = q.front(); q.pop();
      for (Edge e : G[x]) if (level[e.to] == INF && e.cap > 0) {
        level[e.to] = level[x]+1;
        q.push(e.to);
      }
    }
  }
  int maxflow(int s, int t) {
    int flow = 0;
    while (true) {
      bfs(s);
      if (level[t] == INF) return flow;
      while (true) {
        int f = dfs(s, t, INF);
        if (f == 0) break;
        flow += f;
      }
    }
  }
} dinic;

bool color[1000];
bool G[1000][1000];

int findSample(int N, int A[], int host[], int protocol[]) {
  assert(N<=1000);
  rep(i, N) assert(A[i] == 1);
  color[0] = 0;

  for (int i=1; i<N; i++) {
    int p = host[i];
    if (protocol[i] == 0) {
      color[i] = color[p]^1;
      G[i][p] = G[p][i] = true;
    }
    else {
      assert(protocol[i] == 1);
      color[i] = color[p];
      rep(j, N) G[i][j] = G[j][i] = G[p][j];
    }
  }
  vector<int> left, right;
  rep(i, N) if (color[i] == 0) left.pb(i); else right.pb(i);
  int s = N, t = N+1;
  for (int x : left) dinic.add_edge(s, x, 1);
  for (int x : right) dinic.add_edge(x, t, 1);
  for (int x : left) for (int t : right) if (G[x][t]) dinic.add_edge(x, t, 1);
  return N-dinic.maxflow(s, t);
}

• Subtask 1: 0 / 11
• Subtask 2: 0 / 8
• Subtask 3: 0 / 8
• Subtask 4: 0 / 19
• Subtask 5: 23 / 23
• Subtask 6: 0 / 31