Problem p02579 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
using namespace std;
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
// using namespace __gnu_pbds;
/*---------------------DEBUGGING--------------------------------------------*/
void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\\'' << x << '\\''; }
void __print(const char *x) { cerr << '\\"' << x << '\\"'; }
void __print(const string &x) { cerr << '\\"' << x << '\\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }

template <typename T, typename V> void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T> void __print(const T &x) {
  int f = 0;
  cerr << '{';
  for (auto &i : x)
    cerr << (f++ ? "," : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\\n"; }
template <typename T, typename... V> void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v))
    cerr << ", ";
  _print(v...);
}
#ifndef ONLINE_JUDGE
#define debug(x...)                                                            \\
  cerr << "[" << #x << "] = [";                                                \\
  _print(x)
#else
#define debug(x...)
#endif
/*-------------------------------------------------------------------------------------*/
// #define mp make_pair
#define pb push_back
#define ll long long
#define pii pair<int, int>
#define pcc pair<char, char>
#define F first
#define S second
#define int long long
#define pi 3.141592653589793238462643383279502
#define M 1000000007
#define rep(i, a, n) for (int i = a; i < n; i++)
#define INF 10000000000000
#define N 200005
#define vi vector<int>
#define all(v) v.begin(), v.end()
#define endl "\\n"
// #define ordered_set tree<int, null_type,less<int>,
// rb_tree_tag,tree_order_statistics_node_update>
char a[1005][1005];
int dp[1005][1005];
int vis[1005][1005];
int n, m;
int dx[4] = {1, 0, 0, -1};
int dy[4] = {0, -1, 1, 0};
int dx1[24] = {0, 0, 0,  0,  1,  1,  1,  1,  1,  2,  2,  2,
               2, 2, -1, -1, -1, -1, -1, -2, -2, -2, -2, -2};
int dy1[24] = {1,  2,  -1, -2, 0, 1,  2,  -1, -2, 0, 1,  2,
               -1, -2, 0,  1,  2, -1, -2, 0,  1,  2, -1, -2};
bool issafe(int i, int j) {
  if (i >= 1 && i <= n && j >= 1 && j <= m && a[i][j] == '.' && !vis[i][j])
    return true;
  else
    return false;
}
void bfs(int x, int y) {
  priority_queue<pair<int, pii>, vector<pair<int, pii>>,
                 greater<pair<int, pii>>>
      q;
  q.push({0, {x, y}});
  while (!q.empty()) {
    pair<int, pii> p = q.top();
    q.pop();
    if (vis[p.S.F][p.S.S])
      continue;
    int i = p.S.F;
    int j = p.S.S;
    vis[i][j] = 1;
    dp[i][j] = p.F;
    // debug(i,j,dp[i][j]);
    for (int k = 0; k < 4; k++) {
      if (issafe(i + dx[k], j + dy[k])) {
        q.push({p.F, {i + dx[k], j + dy[k]}});
      }
    }
    for (int k = 0; k < 24; k++) {
      if (issafe(i + dx1[k], j + dy1[k])) {
        q.push({p.F + 1, {i + dx1[k], j + dy1[k]}});
      }
    }
  }
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> m;
  int x_s, y_s;
  cin >> x_s >> y_s;
  int x_e, y_e;
  cin >> x_e >> y_e;
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++)
      cin >> a[i][j];
  }
  memset(dp, -1, sizeof(dp));
  bfs(x_s, y_s);
  cout << dp[x_e][y_e] << endl;
}


Error: 0

Fixed submission:

#include <bits/stdc++.h>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
using namespace std;
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
// using namespace __gnu_pbds;
/*---------------------DEBUGGING--------------------------------------------*/
void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\\'' << x << '\\''; }
void __print(const char *x) { cerr << '\\"' << x << '\\"'; }
void __print(const string &x) { cerr << '\\"' << x << '\\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }

template <typename T, typename V> void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T> void __print(const T &x) {
  int f = 0;
  cerr << '{';
  for (auto &i : x)
    cerr << (f++ ? "," : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\\n"; }
template <typename T, typename... V> void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v))
    cerr << ", ";
  _print(v...);
}
#ifndef ONLINE_JUDGE
#define debug(x...)                                                            \\
  cerr << "[" << #x << "] = [";                                                \\
  _print(x)
#else
#define debug(x...)
#endif
/*-------------------------------------------------------------------------------------*/
// #define mp make_pair
#define pb push_back
#define ll long long
#define pii pair<int, int>
#define pcc pair<char, char>
#define F first
#define S second
#define int long long
#define pi 3.141592653589793238462643383279502
#define M 1000000007
#define rep(i, a, n) for (int i = a; i < n; i++)
#define INF 10000000000000
#define N 200005
#define vi vector<int>
#define all(v) v.begin(), v.end()
#define endl "\\n"
// #define ordered_set tree<int, null_type,less<int>,
// rb_tree_tag,tree_order_statistics_node_update>
char a[1005][1005];
int dp[1005][1005];
int vis[1005][1005];
int n, m;
int dx[4] = {1, 0, 0, -1};
int dy[4] = {0, -1, 1, 0};
int dx1[24] = {0, 0, 0,  0,  1,  1,  1,  1,  1,  2,  2,  2,
               2, 2, -1, -1, -1, -1, -1, -2, -2, -2, -2, -2};
int dy1[24] = {1,  2,  -1, -2, 0, 1,  2,  -1, -2, 0, 1,  2,
               -1, -2, 0,  1,  2, -1, -2, 0,  1,  2, -1, -2};
bool issafe(int i, int j) {
  if (i >= 1 && i <= n && j >= 1 && j <= m && a[i][j] == '.' && !vis[i][j])
    return true;
  else
    return false;
}
int dfs(int i, int j, int cnt) {
  vis[i][j] = 1;
  // debug(i,j);
  if (dp[i][j] != -1)
    return dp[i][j];
  dp[i][j] = cnt;
  for (int k = 0; k < 4; k++) {
    if (issafe(i + dx[k], j + dy[k]))
      dfs(i + dx[k], j + dy[k], cnt);
  }
  for (int k = 0; k < 24; k++) {
    if (issafe(i + dx1[k], j + dy1[k]))
      dfs(i + dx1[k], j + dy1[k], cnt + 1);
  }
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> m;
  int x_s, y_s;
  cin >> x_s >> y_s;
  int x_e, y_e;
  cin >> x_e >> y_e;
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++)
      cin >> a[i][j];
  }
  memset(dp, -1, sizeof(dp));
  dfs(x_s, y_s, 0);
  cout << dp[x_e][y_e] << endl;
}