Problem p04007 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <algorithm>
#include <bitset>
#include <cassert>
#include <ciso646>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<ll, ll> P;
typedef tuple<ll, ll, ll> T;
typedef vector<ll> vec;

inline bool check(ll x, ll y, ll xMax, ll yMax) {
  return x >= 0 && y >= 0 && xMax > x && yMax > y;
}
inline int toint(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T> inline string tostring(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}
template <class T> inline T sqr(T x) { return x * x; }
template <class T> inline T mypow(T x, ll n) {
  T res = 1;
  while (n > 0) {
    if (n & 1)
      res = res * x;
    x = x * x;
    n >>= 1;
  }
  return res;
}
inline ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }

#define For(i, a, b) for (ll(i) = (a); i < (b); (i)++)
#define rep(i, n) For(i, 0, n)
#define rFor(i, a, b) for (ll(i) = (a - 1); i >= (b); (i)--)
#define rrep(i, n) rFor(i, n, 0)
#define each(i, n) for (auto &i : n)
#define clr(a) memset((a), 0, sizeof(a))
#define mclr(a) memset((a), -1, sizeof(a))
#define all(a) (a).begin(), (a).end()
#define sz(a) (sizeof(a))
#define tostr(a) tostring(a)
#define dump(val) cerr << #val " = " << val << endl;
#define Fill(a, v) fill((int *)a, (int *)(a + (sz(a) / sz(*(a)))), v)

const ll dx[8] = {1, 0, -1, 0, 1, 1, -1, -1},
         dy[8] = {0, 1, 0, -1, -1, 1, -1, 1};

const ll mod = 1e9 + 7;
const ll INF = 1e17 + 9;

#define int ll
#define double ld

signed main() {
  cin.tie(0);
  ios_base::sync_with_stdio(false);

  int h, w;
  cin >> h >> w;
  vector<string> s(h);

  rep(y, h) { cin >> s[y]; }
  vector<string> red = s, blue = s;

  rep(y, h) rep(x, w) {
    blue[y][x] = '#';
    red[y][x] = '.';
  }

  int y = 0, x = 0;
  int dr = 0;
  int sw = w, sh = h;
  int cnt = 0;

  while (1) {
    bool end = true;
    for (int i = 0;; i++) {
      if (s[y][x] == '.') {
        blue[y][x] = '.';
      }
      red[y][x] = '#';
      int ty = y + dy[dr], tx = x + dx[dr];
      int tty = ty + dy[dr], ttx = tx + dx[dr];
      if (!check(ttx, tty, w, h) ||
          (check(ttx, tty, w, h) && red[tty][ttx] == '#')) {
        break;
      }
      end = false;
      y = ty, x = tx;
    }
    if (end)
      break;
    dr = (dr + 1) % 4;
  }

  rep(y, h) rep(x, w) {
    if (s[y][x] == '#') {
      red[y][x] = '#';
    }
  }

  rep(y, h) { cout << red[y] << endl; }
  cout << endl;
  rep(y, h) { cout << blue[y] << endl; }

  return 0;
}

Fixed submission:
#include <algorithm>
#include <bitset>
#include <cassert>
#include <ciso646>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<ll, ll> P;
typedef tuple<ll, ll, ll> T;
typedef vector<ll> vec;

inline bool check(ll x, ll y, ll xMax, ll yMax) {
  return x >= 0 && y >= 0 && xMax > x && yMax > y;
}
inline int toint(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T> inline string tostring(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}
template <class T> inline T sqr(T x) { return x * x; }
template <class T> inline T mypow(T x, ll n) {
  T res = 1;
  while (n > 0) {
    if (n & 1)
      res = res * x;
    x = x * x;
    n >>= 1;
  }
  return res;
}
inline ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }

#define For(i, a, b) for (ll(i) = (a); i < (b); (i)++)
#define rep(i, n) For(i, 0, n)
#define rFor(i, a, b) for (ll(i) = (a - 1); i >= (b); (i)--)
#define rrep(i, n) rFor(i, n, 0)
#define each(i, n) for (auto &i : n)
#define clr(a) memset((a), 0, sizeof(a))
#define mclr(a) memset((a), -1, sizeof(a))
#define all(a) (a).begin(), (a).end()
#define sz(a) (sizeof(a))
#define tostr(a) tostring(a)
#define dump(val) cerr << #val " = " << val << endl;
#define Fill(a, v) fill((int *)a, (int *)(a + (sz(a) / sz(*(a)))), v)

const ll dx[8] = {1, 0, -1, 0, 1, 1, -1, -1},
         dy[8] = {0, 1, 0, -1, -1, 1, -1, 1};

const ll mod = 1e9 + 7;
const ll INF = 1e17 + 9;

#define int ll
#define double ld

signed main() {
  cin.tie(0);
  ios_base::sync_with_stdio(false);

  int h, w;
  cin >> h >> w;
  vector<string> s(h);

  rep(y, h) { cin >> s[y]; }
  vector<string> red = s, blue = s;

  rep(y, h) rep(x, w) {
    blue[y][x] = '#';
    red[y][x] = '.';
  }

  int y = 0, x = 0;
  int dr = 0;
  int sw = w, sh = h;
  int cnt = 0;

  while (1) {
    bool end = true;
    for (int i = 0;; i++) {
      if (s[y][x] == '.') {
        blue[y][x] = '.';
      }
      red[y][x] = '#';
      int ty = y + dy[dr], tx = x + dx[dr];
      int tty = ty + dy[dr], ttx = tx + dx[dr];
      if ((check(tx, ty, w, h) && red[ty][tx] == '#') ||
          !check(ttx, tty, w, h) ||
          (check(ttx, tty, w, h) && red[tty][ttx] == '#')) {
        break;
      }
      end = false;
      y = ty, x = tx;
    }
    if (end)
      break;
    dr = (dr + 1) % 4;
  }

  rep(y, h) rep(x, w) {
    if (s[y][x] == '#') {
      red[y][x] = '#';
    }
  }

  rep(y, h) { cout << red[y] << endl; }
  cout << endl;
  rep(y, h) { cout << blue[y] << endl; }

  return 0;
}