Submission #2180949

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Source Code Expand

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <string>
#include <cstring>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <cmath>
#include <iomanip>
#include <cassert>
#include <bitset>
using namespace std;

typedef pair<int, int> P;
#define rep(i, n) for (int i=0; i<(n); i++)
#define all(c) (c).begin(), (c).end()
#define uniq(c) c.erase(unique(all(c)), (c).end())
#define index(xs, x) (int)(lower_bound(all(xs), x) - xs.begin())
#define _1 first
#define _2 second
#define pb push_back
#define INF 1145141919
#define MOD 1000000007
struct Dinic {
  #define MAX_V 30000
  struct Edge { int to, cap, rev; };
  vector<Edge> G[MAX_V];
  int level[MAX_V], iter[MAX_V];
  void add_edge(int x, int y, int cap) {
    G[x].pb({ y, cap, (int)G[y].size() });
    G[y].pb({ x, 0, (int)G[x].size()-1 });
  }
  void bfs(int s) {
    rep(i, MAX_V) level[i] = INF;
    queue<int> q;
    q.push(s);
    level[s] = 0;
    while (!q.empty()) {
      int x = q.front(); q.pop();
      for (Edge e : G[x]) {
        if (e.cap > 0 && level[e.to] == INF) {
          level[e.to] = level[x]+1;
          q.push(e.to);
        }
      }
    }
  }
  int dfs(int x, int goal, int f) {
    if (x == goal) return f;
    for (int &i=iter[x]; i<G[x].size(); i++) {
      Edge &e = G[x][i];
      if (e.cap > 0 && level[x] < level[e.to]) {
        int w = dfs(e.to, goal, min(f, e.cap));
        if (w > 0) {
          e.cap -= w;
          G[e.to][e.rev].cap += w;
          return w;
        }
      }
    }
    return 0;
  }
  int max_flow(int s, int t) {
    int flow = 0;
    while (true) {
      bfs(s);
      if (level[t] == INF) return flow;
      rep(i, MAX_V) iter[i] = 0;
      while (true) {
        int f = dfs(s, t, INF);
        if (f == 0) break;
        flow += f;
      }
    }
  }
};
Dinic dinic;

int H, W;
char A[100][100];
int IN[100][100], OUT[100][100];
signed main() {
  ios::sync_with_stdio(false); cin.tie(0);
  cin >> H >> W;
  int V = 0;
  rep(y, H) {
    rep(x, W) {
      cin >> A[x][y];
      if (A[x][y] == 'X') {
        IN[x][y] = OUT[x][y] = V++;
      }
      else {
        IN[x][y] = V++;
        OUT[x][y] = V++;
        dinic.add_edge(IN[x][y], OUT[x][y], 1);
      }
    }
  }
  int s = V++, t = V++;
  rep(x, W) rep(y, H) {
    if (A[x][y] == 'X') dinic.add_edge(s, IN[x][y], INF);
  }
  rep(x, W) rep(y, H) if (x == 0 || x == W-1 || y == 0 || y == H-1) {
    if (A[x][y] == 'X') {
      cout << -1 << "\n";
      return 0;
    }
    dinic.add_edge(OUT[x][y], t, INF);
  }
  rep(x, W-1) rep(y, H) dinic.add_edge(OUT[x][y], IN[x+1][y], INF), dinic.add_edge(OUT[x+1][y], IN[x][y], INF);
  rep(x, W) rep(y, H-1) dinic.add_edge(OUT[x][y], IN[x][y+1], INF), dinic.add_edge(OUT[x][y+1], IN[x][y], INF);
  cout << dinic.max_flow(s, t) << "\n";
  return 0;
}

Submission Info

Judge Result