Language: C++

#include<iostream>
#include<vector>
#include<bits/stdc++.h>
#define lli long long int
#define mod 1000000007
#define pb push_back
#define mk make_pair
#define fastio ios_base::sync_with_stdio(false); cout.tie(NULL);
using namespace std;

char a[1001][1001];
pair<int,int> src,dest;
int n,m,x1,y1,i,j,vis[1001][1001],steps;
vector<pair<int,int>> back_up;
int x[4]={1,-1,0,0};
int y[4]={0,0,1,-1};

bool isValid(int x,int y)
{
	if(x<0 || y<0 || x>=n || y>=m)
		return false;
	if(vis[x][y]==1 || a[x][y]=='#')
		return false;
	return true;	
}

int zeroOneBFS()
{
	queue<pair<int,int>> q;	
	q.push(src);
	vis[src.first][src.second]=1;
	while(!q.empty())
	{
		while(!q.empty())
		{
			pair<int,int> cur=q.front();
			q.pop();
			back_up.pb(cur);
			for(i=0;i<4;i++)
			{
				if(isValid(cur.first+x[i],cur.second+y[i]))
				{
					q.push({cur.first+x[i],cur.second+y[i]});
					vis[cur.first+x[i]][cur.second+y[i]]=1;
					if(cur.first+x[i]==dest.first && cur.second+y[i]==dest.second)
						return steps;	
				}
			}
		}
		for(auto p : back_up)
		{
			for(i=-2;i<=2;i++)
			{
				for(j=-2;j<=2;j++)
				{
					if(isValid(p.first+i,p.second+j))
					{
						q.push({p.first+i,p.second+j});
						vis[p.first+i][p.second+j]=1;
						if(p.first+i==dest.first && p.second+j==dest.second)
							return ++steps;
					}
				}
			}
		}
		steps++;
		back_up.clear();
	}
	return -1;
}

int main()
{
	fastio;
	cin>>n>>m;
	cin>>x1>>y1;
	src={x1-1,y1-1};
	cin>>x1>>y1;
	dest={x1-1,y1-1};
	for(i=0;i<n;i++)
		for(j=0;j<m;j++)
			cin>>a[i][j];
	cout<<zeroOneBFS();
	return 0;
}


Compiler output:
a.cc:13:12: error: 'int y1' redeclared as different kind of entity
   13 | int n,m,x1,y1,i,j,vis[1001][1001],steps;
      |            ^~
In file included from /usr/include/features.h:523,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/os_defines.h:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/c++config.h:683,
                 from /usr/include/c++/14/bits/requires_hosted.h:31,
                 from /usr/include/c++/14/iostream:38,
                 from a.cc:1:
/usr/include/x86_64-linux-gnu/bits/mathcalls.h:257:1: note: previous declaration 'double y1(double)'
  257 | __MATHCALL (y1,, (_Mdouble_));
      | ^~~~~~~~~~
a.cc: In function 'int main()':
a.cc:76:16: error: no match for 'operator>>' (operand types are 'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} and 'double(double) noexcept')
   76 |         cin>>x1>>y1;
      |         ~~~~~~~^~~~
      |            |     |
      |            |     double(double) noexcept
      |            std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}
In file included from /usr/include/c++/14/iostream:42:
/usr/include/c++/14/istream:170:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  170 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:170:7: note:   conversion of argument 1 would be ill-formed:
a.cc:76:18: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'double (*)(double) noexcept'
   76 |         cin>>x1>>y1;
      |                  ^~
/usr/include/c++/14/istream:174:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  174 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:174:7: note:   conversion of argument 1 would be ill-formed:
a.cc:76:18: error: invalid conversion from 'double (*)(double) noexcept' to 'short int' [-fpermissive]
   76 |         cin>>x1>>y1;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept
a.cc:76:18: error: cannot bind rvalue '(short int)y1' to 'short int&'
/usr/include/c++/14/istream:177:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  177 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:177:7: note:   conversion of argument 1 would be ill-formed:
a.cc:76:18: error: invalid conversion from 'double (*)(double) noexcept' to 'short unsigned int' [-fpermissive]
   76 |         cin>>x1>>y1;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept
a.cc:76:18: error: cannot bind rvalue '(short unsigned int)y1' to 'short unsigned int&'
/usr/include/c++/14/istream:181:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  181 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:181:7: note:   conversion of argument 1 would be ill-formed:
a.cc:76:18: error: invalid conversion from 'double (*)(double) noexcept' to 'int' [-fpermissive]
   76 |         cin>>x1>>y1;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept
a.cc:76:18: error: cannot bind rvalue '(int)y1' to 'int&'
/usr/include/c++/14/istream:184:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  184 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:184:7: note:   conversion of argument 1 would be ill-formed:
a.cc:76:18: error: invalid conversion from 'double (*)(double) noexcept' to 'unsigned int' [-fpermissive]
   76 |         cin>>x1>>y1;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept
a.cc:76:18: error: cannot bind rvalue '(unsigned int)y1' to 'unsigned int&'
/usr/include/c++/14/istream:188:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  188 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:188:7: note:   conversion of argument 1 would be ill-formed:
a.cc:76:18: error: invalid conversion from 'double (*)(double) noexcept' to 'long int' [-fpermissive]
   76 |         cin>>x1>>y1;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept
a.cc:76:18: error: cannot bind rvalue '(long int)y1' to 'long int&'
/usr/include/c++/14/istream:192:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  192 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:192:7: note:   conversion of argument 1 would be ill-formed:
a.cc:76:18: error: invalid conversion from 'double (*)(double) noexcept' to 'long unsigned int' [-fpermissive]
   76 |         cin>>x1>>y1;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept
a.cc:76:18: error: cannot bind rvalue '(long unsigned int)y1' to 'long unsigned int&'
/usr/include/c++/14/istream:199:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  199 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:199:7: note:   conversion of argument 1 would be ill-formed:
a.cc:76:18: error: invalid conversion from 'double (*)(double) noexcept' to 'long long int' [-fpermissive]
   76 |         cin>>x1>>y1;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept
a.cc:76:18: error: cannot bind rvalue '(long long int)y1' to 'long long int&'
/usr/include/c++/14/istream:203:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  203 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:203:7: note:   conversion of argument 1 would be ill-formed:
a.cc:76:18: error: invalid conversion from 'double (*)(double) noexcept' to 'long long unsigned int' [-fpermissive]
   76 |         cin>>x1>>y1;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept
a.cc:76:18: error: cannot bind rvalue '(long long unsigned int)y1' to 'long long unsigned int&'
/usr/include/c++/14/istream:328:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  328 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/14/istream:328:7: note:   conversion of argument 1 would be ill-formed:
a.cc:76:18: error: invalid conversion from 'double (*)(double) noexcept' to 'void*' [-fpermissive]
   76 |         cin>>x1>>y1;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept
a.cc:76:18: error: cannot bind rvalue '(void*)y1' to 'void*&'
/usr/include/c++/14/istream:122:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__istream_type& (*)(__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:122:7: note:   conversion of argument 1 would be ill-formed:
a.cc:76:18: error: invalid conversion from 'double (*)(double) noexcept' to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&)' {aka 'std::basic_istream<char>& (*)(std::basic_istream<char>&)'} [-fpermissive]
   76 |         cin>>x1>>y1;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept
/usr/include/c++/14/istream:126:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__ios_type& (*)(__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>; __ios_type = std::basic_ios<char>]' (near match)
  126 |       operator>>(__ios_type& (*__pf)(__ios_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:126:7: note:   conversion of argument 1 would be ill-formed:
a.cc:76:18: error: invalid conversion from 'double (*)(double) noexcept' to 'std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&)' {aka 'std::basic_ios<char>& (*)(std::basic_ios<char>&)'} [-fpermissive]
   76 |         cin>>x1>>y1;
      |                  ^~
      |                  |
      |                  double (*)(double) noexcept
/usr/include/c++/14/istream:133:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istrea