Problem p02644 (C++)

Buggy submission (status: Time Limit Exceeded):
// c++ -std=gnu++14 a.cpp
#include <algorithm>
#include <bitset>
#include <climits>
#include <complex>
#include <deque>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <istream>
#include <iterator>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
// typedef pair<ll, ll> P;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define revrep(i, n) for (int i = (n)-1; i >= 0; i--)
#define pb push_back
#define f first
#define s second
#define chmin(x, y) x = min(x, y);
#define chmax(x, y) x = max(x, y);
#define sz(x) ((int)(x).size())

// const ll INFL = LLONG_MAX;//10^18 = 2^60
const ll INFL = 1LL << 60;
// const int INF = INT_MAX;
const int INF = 1 << 30; // 10^9
const ll MOD = 1000000007;
// const ll MOD = 998244353;
double EPS = 1e-10;

vector<ll> dy = {0, 1, 0, -1, 1, 1, -1, -1, 0};
vector<ll> dx = {1, 0, -1, 0, 1, -1, 1, -1, 0};

void pres(double A) { printf("%.9lf\n", A); }
void BinarySay(ll x, ll y = 60) {
  rep(i, y) cout << (x >> (y - 1 - i) & 1);
  cout << endl;
}
ll cnt_bit(ll x) { return __builtin_popcountll(x); }

ll pow_long(ll x, ll k) {
  ll res = 1;
  while (k > 0) {
    if (k % 2)
      res *= x;
    x *= x;
    k /= 2;
  }
  return res;
}

ll pow_mod(ll x, ll k) {
  ll res = 1;
  while (k > 0) {
    if (k % 2) {
      res *= x;
      res %= MOD;
    }
    x *= x;
    x %= MOD;
    k /= 2;
  }
  return res;
}

ll inverse(ll x) { return pow_mod(x, MOD - 2); };

ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}

ll lcm(ll x, ll y) {
  ll res = x / gcd(x, y);
  res *= y;
  return res;
};

// コンビネーション
const int MAXcomb = 2000010;
ll fac[MAXcomb], finv[MAXcomb], inv[MAXcomb];
// facはn!,finvは1/n!
// invは逆元
void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAXcomb; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
ll comb(int n, int k) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  return fac[n] * finv[k] % MOD * finv[n - k] % MOD;
}

const int MAXkai = 500010;
ll kai_memo[MAXkai];
ll kai(ll N) {
  if (kai_memo[N] != 0)
    return kai_memo[N];
  if (N <= 1)
    return 1;
  return kai_memo[N] = N * kai(N - 1) % MOD;
}

ll disit(ll s, ll base = 10) {
  ll res = 0;
  while (s) {
    res++;
    s /= base;
  }
  return res;
}

vector<int> divisor(int n) {
  vector<int> res(0);
  for (int i = 1; i * i <= n; i++) {
    if (n % i == 0) {
      res.push_back(i);
      if (i != n / i)
        res.push_back(n / i);
    }
  }
  sort(res.begin(), res.end());
  return res;
}

int H, W, K;
int sx, sy, tx, ty;
vector<vector<bool>> C;
vector<vector<int>> dist;

bool in(int x, int y) {
  if (x >= 0 && x < H && y >= 0 && y < W)
    return true;
  return false;
}

void solve() {
  cin >> H >> W >> K;
  cin >> sx >> sy >> tx >> ty;
  sx--, sy--, tx--, ty--;
  C.resize(H);
  rep(i, H) { C[i].resize(W, false); }
  dist.resize(H);
  rep(i, H) { dist[i].resize(W, false); }

  rep(i, H) rep(j, W) {
    char c;
    cin >> c;
    if (c == '.')
      C[i][j] = true;
    dist[i][j] = INF;
  }
  queue<pair<int, int>> Q;
  dist[sx][sy] = 0;
  Q.push({sx, sy});
  while (Q.size()) {
    pair<int, int> n = Q.front();
    Q.pop();
    int nx = n.f;
    int ny = n.s;
    for (int i = 0; i < 4; i++) {
      for (int j = 1; j <= K; j++) {
        int nnx = nx + dx[i] * j;
        int nny = ny + dy[i] * j;
        if (!in(nnx, nny))
          break;
        if (!C[nnx][nny])
          break;
        if (dist[nnx][nny] <= dist[nx][ny])
          break;
        dist[nnx][nny] = dist[nx][ny] + 1;
        Q.push({nnx, nny});
      }
    }
  }
  int ans = dist[tx][ty];
  if (ans == INF)
    ans = -1;
  cout << ans << endl;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  solve();
}


Fixed submission:
// c++ -std=gnu++14 a.cpp
#include <algorithm>
#include <bitset>
#include <climits>
#include <complex>
#include <deque>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <istream>
#include <iterator>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
// typedef pair<ll, ll> P;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define revrep(i, n) for (int i = (n)-1; i >= 0; i--)
#define pb push_back
#define f first
#define s second
#define chmin(x, y) x = min(x, y);
#define chmax(x, y) x = max(x, y);
#define sz(x) ((int)(x).size())

// const ll INFL = LLONG_MAX;//10^18 = 2^60
const ll INFL = 1LL << 60;
// const int INF = INT_MAX;
const int INF = 1 << 30; // 10^9
const ll MOD = 1000000007;
// const ll MOD = 998244353;
double EPS = 1e-10;

vector<ll> dy = {0, 1, 0, -1, 1, 1, -1, -1, 0};
vector<ll> dx = {1, 0, -1, 0, 1, -1, 1, -1, 0};

void pres(double A) { printf("%.9lf\n", A); }
void BinarySay(ll x, ll y = 60) {
  rep(i, y) cout << (x >> (y - 1 - i) & 1);
  cout << endl;
}
ll cnt_bit(ll x) { return __builtin_popcountll(x); }

ll pow_long(ll x, ll k) {
  ll res = 1;
  while (k > 0) {
    if (k % 2)
      res *= x;
    x *= x;
    k /= 2;
  }
  return res;
}

ll pow_mod(ll x, ll k) {
  ll res = 1;
  while (k > 0) {
    if (k % 2) {
      res *= x;
      res %= MOD;
    }
    x *= x;
    x %= MOD;
    k /= 2;
  }
  return res;
}

ll inverse(ll x) { return pow_mod(x, MOD - 2); };

ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}

ll lcm(ll x, ll y) {
  ll res = x / gcd(x, y);
  res *= y;
  return res;
};

// コンビネーション
const int MAXcomb = 2000010;
ll fac[MAXcomb], finv[MAXcomb], inv[MAXcomb];
// facはn!,finvは1/n!
// invは逆元
void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAXcomb; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
ll comb(int n, int k) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  return fac[n] * finv[k] % MOD * finv[n - k] % MOD;
}

const int MAXkai = 500010;
ll kai_memo[MAXkai];
ll kai(ll N) {
  if (kai_memo[N] != 0)
    return kai_memo[N];
  if (N <= 1)
    return 1;
  return kai_memo[N] = N * kai(N - 1) % MOD;
}

ll disit(ll s, ll base = 10) {
  ll res = 0;
  while (s) {
    res++;
    s /= base;
  }
  return res;
}

vector<int> divisor(int n) {
  vector<int> res(0);
  for (int i = 1; i * i <= n; i++) {
    if (n % i == 0) {
      res.push_back(i);
      if (i != n / i)
        res.push_back(n / i);
    }
  }
  sort(res.begin(), res.end());
  return res;
}

int H, W, K;
int sx, sy, tx, ty;
vector<vector<bool>> C;
vector<vector<int>> dist;

bool in(int x, int y) {
  if (x >= 0 && x < H && y >= 0 && y < W)
    return true;
  return false;
}

void solve() {
  cin >> H >> W >> K;
  cin >> sx >> sy >> tx >> ty;
  sx--, sy--, tx--, ty--;
  C.resize(H);
  rep(i, H) { C[i].resize(W, false); }
  dist.resize(H);
  rep(i, H) { dist[i].resize(W, false); }

  rep(i, H) rep(j, W) {
    char c;
    cin >> c;
    if (c == '.')
      C[i][j] = true;
    dist[i][j] = INF;
  }
  queue<pair<int, int>> Q;
  dist[sx][sy] = 0;
  Q.push({sx, sy});
  while (Q.size()) {
    pair<int, int> n = Q.front();
    Q.pop();
    int nx = n.f;
    int ny = n.s;
    for (int i = 0; i < 4; i++) {
      for (int j = 1; j <= K; j++) {
        int nnx = nx + dx[i] * j;
        int nny = ny + dy[i] * j;
        if (!in(nnx, nny))
          break;
        if (!C[nnx][nny])
          break;
        if (dist[nnx][nny] <= dist[nx][ny])
          break;
        if (dist[nnx][nny] > dist[nx][ny] + 1) {
          dist[nnx][nny] = dist[nx][ny] + 1;
          Q.push({nnx, nny});
        }
      }
    }
  }
  int ans = dist[tx][ty];
  if (ans == INF)
    ans = -1;
  cout << ans << endl;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  solve();
}