Problem p02579 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define ALL(x) x.begin(), x.end()
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
using namespace std;
random_device rnd;
mt19937 mt(rnd());
using ll = long long;
using lld = long double;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;
using PII = pair<int, int>;
const int IINF = 1 << 30;
const ll INF = 1ll << 60;
const ll MOD = 1000000007;
int h, w;

vector<int> dijkstra(map<int, vector<pair<int, int>>> &g, int start) {
  ll n = h * w;
  priority_queue<pair<int, int>, vector<pair<int, int>>,
                 greater<pair<int, int>>>
      pque;
  pque.push({0, start});
  vector<int> ret(n + 2, IINF);
  while (!pque.empty()) {
    auto cost = pque.top().first;
    auto cur = pque.top().second;
    pque.pop();
    if (ret[cur] <= cost)
      continue;
    ret[cur] = cost;
    for (auto &&x : g[cur]) {
      int next = x.first;
      ll d = x.second;
      if (cost + d < ret[next])
        pque.push({cost + d, next});
    }
  }

  return ret;
}

bool is_valid(int y, int x) { return 0 <= y && y < h && 0 <= x && x < w; }

int main() {
  cin >> h >> w;
  int sy, sx, gy, gx;
  cin >> sy >> sx >> gy >> gx;
  sy--;
  sx--;
  gy--;
  gx--;
  vector<string> g(h);
  rep(i, h) { cin >> g[i]; }
  map<int, vector<pair<int, int>>> graph;
  rep(y, h) {
    rep(x, w) {
      int dx[5] = {-2, -1, 0, 1, 2};
      int dy[5] = {-2, -1, 0, 1, 2};
      rep(i, 5) rep(j, 5) {
        if (dy[i] == 0 && dx[j] == 0)
          continue;
        int ny = y + dy[i];
        int nx = x + dx[j];

        if (is_valid(ny, nx) && g[ny][nx] == '.') {
          if ((dy[i] == 1 && dx[j] == 0) || (dy[i] == -1 && dx[j] == 0) ||
              (dy[i] == 0 && dx[j] == 1) || (dy[i] == 0 && dx[j] == -1)) {
            graph[w * y + x].push_back({w * ny + nx, 0});
          } else {
            graph[w * y + x].push_back({w * ny + nx, 1});
          }
        }
      }
    }
  }
  auto cost = dijkstra(graph, w * sy + sx);
  if (cost[w * gy + gx] == IINF) {
    cout << -1 << endl;
  } else {
    cout << cost[w * gy + gx] << endl;
  }
  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define ALL(x) x.begin(), x.end()
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
using namespace std;
random_device rnd;
mt19937 mt(rnd());
using ll = long long;
using lld = long double;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;
using PII = pair<int, int>;
const int IINF = 1 << 30;
const ll INF = 1ll << 60;
const ll MOD = 1000000007;
int h, w;

vector<int> dijkstra(map<int, vector<pair<int, int>>> &g, int start) {
  ll n = h * w;
  priority_queue<pair<int, int>, vector<pair<int, int>>,
                 greater<pair<int, int>>>
      pque;
  pque.push({0, start});
  vector<int> ret(n + 2, IINF);
  while (!pque.empty()) {
    auto cost = pque.top().first;
    auto cur = pque.top().second;
    pque.pop();
    if (ret[cur] <= cost)
      continue;
    ret[cur] = cost;
    for (auto &&x : g[cur]) {
      int next = x.first;
      ll d = x.second;
      if (cost + d < ret[next])
        pque.push({cost + d, next});
    }
  }

  return ret;
}

bool is_valid(int y, int x) { return 0 <= y && y < h && 0 <= x && x < w; }

int main() {
  cin >> h >> w;
  int sy, sx, gy, gx;
  cin >> sy >> sx >> gy >> gx;
  sy--;
  sx--;
  gy--;
  gx--;
  vector<string> g(h);
  rep(i, h) { cin >> g[i]; }
  map<int, vector<pair<int, int>>> graph;
  rep(y, h) {
    rep(x, w) {
      int dx[5] = {-2, -1, 0, 1, 2};
      int dy[5] = {-2, -1, 0, 1, 2};
      rep(i, 5) rep(j, 5) {
        if (dy[i] == 0 && dx[j] == 0)
          continue;
        int ny = y + dy[i];
        int nx = x + dx[j];

        if (is_valid(ny, nx) && g[ny][nx] == '.') {
          if ((dy[i] == 1 && dx[j] == 0) || (dy[i] == -1 && dx[j] == 0) ||
              (dy[i] == 0 && dx[j] == 1) || (dy[i] == 0 && dx[j] == -1)) {
            graph[w * y + x].push_back({w * ny + nx, 0});
          } else {
            graph[w * y + x].push_back({w * ny + nx, 1});
          }
        }
      }
    }
  }

  ll n = h * w;
  int start = (w * sy) + sx;
  priority_queue<pair<int, int>, vector<pair<int, int>>,
                 greater<pair<int, int>>>
      pque;
  pque.push({0, start});
  vector<int> ret(n + 2, IINF);
  while (!pque.empty()) {
    auto cost = pque.top().first;
    auto cur = pque.top().second;
    pque.pop();
    if (ret[cur] <= cost)
      continue;
    ret[cur] = cost;
    for (auto &&x : graph[cur]) {
      int next = x.first;
      ll d = x.second;
      if (cost + d < ret[next])
        pque.push({cost + d, next});
    }
  }

  auto cost = ret;
  if (cost[w * gy + gx] == IINF) {
    cout << -1 << endl;
  } else {
    cout << cost[w * gy + gx] << endl;
  }
  return 0;
}