Problem p02542 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
// #pragma GCC optimize("Ofast")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

#define ms(s, n) memset(s, n, sizeof(s))
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define FORd(i, a, b) for (int i = (a)-1; i >= (b); --i)
#define FORall(it, a)                                                          \
  for (__typeof((a).begin()) it = (a).begin(); it != (a).end(); it++)
#define sz(a) int((a).size())
#define present(t, x) (t.find(x) != t.end())
#define all(a) (a).begin(), (a).end()
#define uni(a) (a).erase(unique(all(a)), (a).end())
#define pb push_back
#define pf push_front
#define mp make_pair
#define fi first
#define se second
#define prec(n) fixed << setprecision(n)
#define bit(n, i) (((n) >> (i)) & 1)
#define bitcount(n) __builtin_popcountll(n)
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pi;
typedef vector<int> vi;
typedef vector<pi> vii;
const int MOD = (int)1e9 + 7;
const int FFTMOD = 119 << 23 | 1;
const int INF = (int)1e9 + 23111992;
const ll LINF = (ll)1e18 + 23111992;
const ld PI = acos((ld)-1);
const ld EPS = 1e-9;
inline ll gcd(ll a, ll b) {
  ll r;
  while (b) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
inline ll fpow(ll n, ll k, int p = MOD) {
  ll r = 1;
  for (; k; k >>= 1) {
    if (k & 1)
      r = r * n % p;
    n = n * n % p;
  }
  return r;
}
template <class T> inline int chkmin(T &a, const T &val) {
  return val < a ? a = val, 1 : 0;
}
template <class T> inline int chkmax(T &a, const T &val) {
  return a < val ? a = val, 1 : 0;
}
inline ull isqrt(ull k) {
  ull r = sqrt(k) + 1;
  while (r * r > k)
    r--;
  return r;
}
inline ll icbrt(ll k) {
  ll r = cbrt(k) + 1;
  while (r * r * r > k)
    r--;
  return r;
}
inline void addmod(int &a, int val, int p = MOD) {
  if ((a = (a + val)) >= p)
    a -= p;
}
inline void submod(int &a, int val, int p = MOD) {
  if ((a = (a - val)) < 0)
    a += p;
}
inline int mult(int a, int b, int p = MOD) { return (ll)a * b % p; }
inline int inv(int a, int p = MOD) { return fpow(a, p - 2, p); }
inline int sign(ld x) { return x < -EPS ? -1 : x > +EPS; }
inline int sign(ld x, ld y) { return sign(x - y); }
mt19937 mt(chrono::high_resolution_clock::now().time_since_epoch().count());
inline int mrand() { return abs((int)mt()); }
inline int mrand(int k) { return abs((int)mt()) % k; }
#define db(x) cerr << "[" << #x << ": " << (x) << "] ";
#define endln cerr << "\n";

#define MF MincostMaxflow
#define flow_t int
#define cost_t long long
const flow_t foo = (flow_t)1e9;
const cost_t coo = (cost_t)1e18;
namespace MincostMaxflow {
const int maxv = 2e6 + 5;
const int maxe = 2e6 + 5;
int n, s, t, E;
int adj[maxe], nxt[maxe], lst[maxv], frm[maxv], vis[maxv];
flow_t cap[maxe], flw[maxe], totalFlow;
cost_t cst[maxe], dst[maxv], totalCost;

void init(int nn, int ss, int tt) {
  n = nn, s = ss, t = tt;
  fill_n(lst, n, -1), E = 0;
}
void add(int u, int v, flow_t ca, cost_t co) {
  adj[E] = v, cap[E] = ca, flw[E] = 0, cst[E] = +co, nxt[E] = lst[u],
  lst[u] = E++;
  adj[E] = u, cap[E] = 0, flw[E] = 0, cst[E] = -co, nxt[E] = lst[v],
  lst[v] = E++;
}
int spfa() {
  fill_n(dst, n, coo), dst[s] = 0;
  queue<int> que;
  que.push(s);
  while (que.size()) {
    int u = que.front();
    que.pop();
    for (int e = lst[u]; e != -1; e = nxt[e])
      if (flw[e] < cap[e]) {
        int v = adj[e];
        if (dst[v] > dst[u] + cst[e]) {
          dst[v] = dst[u] + cst[e];
          frm[v] = e;
          if (!vis[v]) {
            vis[v] = 1;
            que.push(v);
          }
        }
      }
    vis[u] = 0;
  }
  return dst[t] < coo;
}
cost_t mincost() {
  totalCost = 0, totalFlow = 0;
  while (1) {
    if (!spfa())
      break;
    flow_t mn = foo;
    for (int v = t, e = frm[v]; v != s; v = adj[e ^ 1], e = frm[v])
      mn = min(mn, cap[e] - flw[e]);
    for (int v = t, e = frm[v]; v != s; v = adj[e ^ 1], e = frm[v]) {
      flw[e] += mn;
      flw[e ^ 1] -= mn;
    }
    totalFlow += mn;
    totalCost += mn * dst[t];
  }
  return totalCost;
}
} // namespace MincostMaxflow

void chemthan() {
  int n, m;
  cin >> n >> m;
  vector<string> s(n);
  FOR(i, 0, n) cin >> s[i];
  int tot = n * m * 2;
  int S = tot++, t = tot++;
  MF::init(tot, S, t);
  int num = 0;
  FOR(i, 0, n) FOR(j, 0, m) if (s[i][j] == 'o') {
    MF::add(S, i * m + j, 1, 0);
    num++;
    vector<vi> dp(n, vi(m, INF));
    queue<int> que;
    dp[i][j] = 0, que.push(i), que.push(j);
    while (sz(que)) {
      int u = que.front();
      que.pop();
      int v = que.front();
      que.pop();
      if (u + 1 < n && s[u + 1][v] != '#') {
        if (chkmin(dp[u + 1][v], dp[u][v] + 1)) {
          que.push(u + 1), que.push(v);
        }
      }
      if (v + 1 < n && s[u][v + 1] != '#') {
        if (chkmin(dp[u][v + 1], dp[u][v] + 1)) {
          que.push(u), que.push(v + 1);
        }
      }
    }
    vector<tuple<int, int, int>> vals;
    FOR(u, 0, n) FOR(v, 0, m) if (dp[u][v] < INF) {
      MF::add(i * m + j, n * m + u * m + v, 1, 100000 - dp[u][v]);
    }
  }
  FOR(i, 0, n * m) { MF::add(n * m + i, t, 1, 0); }
  cout << (long long)100000 * num - MF::mincost() << "\n";
}

int32_t main(int32_t argc, char *argv[]) {
  ios_base::sync_with_stdio(0), cin.tie(0);
  if (argc > 1) {
    assert(freopen(argv[1], "r", stdin));
  }
  if (argc > 2) {
    assert(freopen(argv[2], "wb", stdout));
  }
  chemthan();
  cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
// #pragma GCC optimize("Ofast")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

#define ms(s, n) memset(s, n, sizeof(s))
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define FORd(i, a, b) for (int i = (a)-1; i >= (b); --i)
#define FORall(it, a)                                                          \
  for (__typeof((a).begin()) it = (a).begin(); it != (a).end(); it++)
#define sz(a) int((a).size())
#define present(t, x) (t.find(x) != t.end())
#define all(a) (a).begin(), (a).end()
#define uni(a) (a).erase(unique(all(a)), (a).end())
#define pb push_back
#define pf push_front
#define mp make_pair
#define fi first
#define se second
#define prec(n) fixed << setprecision(n)
#define bit(n, i) (((n) >> (i)) & 1)
#define bitcount(n) __builtin_popcountll(n)
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pi;
typedef vector<int> vi;
typedef vector<pi> vii;
const int MOD = (int)1e9 + 7;
const int FFTMOD = 119 << 23 | 1;
const int INF = (int)1e9 + 23111992;
const ll LINF = (ll)1e18 + 23111992;
const ld PI = acos((ld)-1);
const ld EPS = 1e-9;
inline ll gcd(ll a, ll b) {
  ll r;
  while (b) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
inline ll fpow(ll n, ll k, int p = MOD) {
  ll r = 1;
  for (; k; k >>= 1) {
    if (k & 1)
      r = r * n % p;
    n = n * n % p;
  }
  return r;
}
template <class T> inline int chkmin(T &a, const T &val) {
  return val < a ? a = val, 1 : 0;
}
template <class T> inline int chkmax(T &a, const T &val) {
  return a < val ? a = val, 1 : 0;
}
inline ull isqrt(ull k) {
  ull r = sqrt(k) + 1;
  while (r * r > k)
    r--;
  return r;
}
inline ll icbrt(ll k) {
  ll r = cbrt(k) + 1;
  while (r * r * r > k)
    r--;
  return r;
}
inline void addmod(int &a, int val, int p = MOD) {
  if ((a = (a + val)) >= p)
    a -= p;
}
inline void submod(int &a, int val, int p = MOD) {
  if ((a = (a - val)) < 0)
    a += p;
}
inline int mult(int a, int b, int p = MOD) { return (ll)a * b % p; }
inline int inv(int a, int p = MOD) { return fpow(a, p - 2, p); }
inline int sign(ld x) { return x < -EPS ? -1 : x > +EPS; }
inline int sign(ld x, ld y) { return sign(x - y); }
mt19937 mt(chrono::high_resolution_clock::now().time_since_epoch().count());
inline int mrand() { return abs((int)mt()); }
inline int mrand(int k) { return abs((int)mt()) % k; }
#define db(x) cerr << "[" << #x << ": " << (x) << "] ";
#define endln cerr << "\n";

#define MF MincostMaxflow
#define flow_t int
#define cost_t long long
const flow_t foo = (flow_t)1e9;
const cost_t coo = (cost_t)1e18;
namespace MincostMaxflow {
const int maxv = 2e6 + 5;
const int maxe = 2e6 + 5;
int n, s, t, E;
int adj[maxe], nxt[maxe], lst[maxv], frm[maxv], vis[maxv];
flow_t cap[maxe], flw[maxe], totalFlow;
cost_t cst[maxe], dst[maxv], totalCost;

void init(int nn, int ss, int tt) {
  n = nn, s = ss, t = tt;
  fill_n(lst, n, -1), E = 0;
}
void add(int u, int v, flow_t ca, cost_t co) {
  adj[E] = v, cap[E] = ca, flw[E] = 0, cst[E] = +co, nxt[E] = lst[u],
  lst[u] = E++;
  adj[E] = u, cap[E] = 0, flw[E] = 0, cst[E] = -co, nxt[E] = lst[v],
  lst[v] = E++;
}
int spfa() {
  fill_n(dst, n, coo), dst[s] = 0;
  queue<int> que;
  que.push(s);
  while (que.size()) {
    int u = que.front();
    que.pop();
    for (int e = lst[u]; e != -1; e = nxt[e])
      if (flw[e] < cap[e]) {
        int v = adj[e];
        if (dst[v] > dst[u] + cst[e]) {
          dst[v] = dst[u] + cst[e];
          frm[v] = e;
          if (!vis[v]) {
            vis[v] = 1;
            que.push(v);
          }
        }
      }
    vis[u] = 0;
  }
  return dst[t] < coo;
}
cost_t mincost() {
  totalCost = 0, totalFlow = 0;
  while (1) {
    if (!spfa())
      break;
    flow_t mn = foo;
    for (int v = t, e = frm[v]; v != s; v = adj[e ^ 1], e = frm[v])
      mn = min(mn, cap[e] - flw[e]);
    for (int v = t, e = frm[v]; v != s; v = adj[e ^ 1], e = frm[v]) {
      flw[e] += mn;
      flw[e ^ 1] -= mn;
    }
    totalFlow += mn;
    totalCost += mn * dst[t];
  }
  return totalCost;
}
} // namespace MincostMaxflow

void chemthan() {
  int n, m;
  cin >> n >> m;
  vector<string> s(n);
  FOR(i, 0, n) cin >> s[i];
  int tot = n * m * 2;
  int S = tot++, t = tot++;
  MF::init(tot, S, t);
  int num = 0;
  FOR(i, 0, n) FOR(j, 0, m) if (s[i][j] == 'o') {
    MF::add(S, i * m + j, 1, 0);
    num++;
    vector<vi> dp(n, vi(m, INF));
    queue<int> que;
    dp[i][j] = 0, que.push(i), que.push(j);
    while (sz(que)) {
      int u = que.front();
      que.pop();
      int v = que.front();
      que.pop();
      if (u + 1 < n && s[u + 1][v] != '#') {
        if (chkmin(dp[u + 1][v], dp[u][v] + 1)) {
          que.push(u + 1), que.push(v);
        }
      }
      if (v + 1 < m && s[u][v + 1] != '#') {
        if (chkmin(dp[u][v + 1], dp[u][v] + 1)) {
          que.push(u), que.push(v + 1);
        }
      }
    }
    vector<tuple<int, int, int>> vals;
    FOR(u, 0, n) FOR(v, 0, m) if (dp[u][v] < INF) {
      MF::add(i * m + j, n * m + u * m + v, 1, 100000 - dp[u][v]);
    }
  }
  FOR(i, 0, n * m) { MF::add(n * m + i, t, 1, 0); }
  cout << (long long)100000 * num - MF::mincost() << "\n";
}

int32_t main(int32_t argc, char *argv[]) {
  ios_base::sync_with_stdio(0), cin.tie(0);
  if (argc > 1) {
    assert(freopen(argv[1], "r", stdin));
  }
  if (argc > 2) {
    assert(freopen(argv[2], "wb", stdout));
  }
  chemthan();
  cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
  return 0;
}