Submission #26197

#	Time	Username	Problem	Language	Result	Execution time	Memory
26197		samir_droubi	Portals (BOI14_portals)	C++14	70 / 100	1000 ms	145192 KiB

portals

#pragma optimize("O3")
#include <bits/stdc++.h>
using namespace std;
const int mxn=1005;
int n,m;
char g[mxn][mxn];

int dx[]={0,0,1,-1};
int dy[]={1,-1,0,0};
bool check(int x,int y){
	return x>=1&&x<=n&&y>=1&&y<=m&&g[x][y]!='#';
}

int wall[mxn][mxn];
queue<pair<int,int> >q;
void bfs()
{
	while(!q.empty())
	{
		int x=q.front().first;
		int y=q.front().second;
		q.pop();
		for(int i=0;i<4;++i)
		{
			int xx=x+dx[i];
			int yy=y+dy[i];
			if(!check(xx,yy))continue;
			if(wall[xx][yy]>wall[x][y]+1)
			{
				wall[xx][yy]=wall[x][y]+1;
				q.push({xx,yy});
			}
		}
	}
}

vector<pair<pair<int,int>,int> >adj[mxn][mxn];;
int dist[mxn][mxn];
set<pair<int,pair<int,int> > >pq;
void dijkstra(int x,int y)
{
	dist[x][y]=0;
	pq.insert({0,{x,y}});
	while(!pq.empty())
	{
		pair<int,pair<int,int> > p=*pq.begin();
		pq.erase(pq.begin());
		int ds=p.first;
		int x=p.second.first;
		int y=p.second.second;
		for(int i=0;i<adj[x][y].size();++i)
		{
			int xx=adj[x][y][i].first.first;
			int yy=adj[x][y][i].first.second;
			int w=adj[x][y][i].second;
			if(dist[xx][yy]>ds+w)
			{
				dist[xx][yy]=ds+w;
				pq.insert({ds+w,{xx,yy}});
			}
		}		
	}
}

void clear()
{
	for(int i=0;i<mxn;++i)
		for(int j=0;j<mxn;++j)
		{
			wall[i][j]=(1e9);
			dist[i][j]=(1e9);
		}
}
void up(int i,int j)
{
	int x=i;
	while(x>=1&&g[x][j]!='#')
	{
		adj[x][j].push_back({{i,j},wall[x][j]});
		--x;
	}
}
void down(int i,int j)
{
	int x=i;
	while(x<=n&&g[x][j]!='#')
	{
		adj[x][j].push_back({{i,j},wall[x][j]});
		++x;
	}
}
void left(int i,int j)
{
	int y=j;
	while(y>=1&&g[i][y]!='#')
	{
		adj[i][y].push_back({{i,j},wall[i][y]});
		--y;
	}
}
void right(int i,int j)
{
	int y=j;
	while(y<=m&&g[i][y]!='#')
	{
		adj[i][y].push_back({{i,j},wall[i][y]});
		++y;
	}
}
int main()
{
	clear();
	int sx,sy,ex,ey;
	scanf("%d%d",&n,&m);
	for(int i=1;i<=n;++i)
		for(int j=1;j<=m;++j)
		{
			cin>>g[i][j];
			if(g[i][j]=='S')
			{
				sx=i;
				sy=j;
			}
			if(g[i][j]=='C')
			{
				ex=i;
				ey=j;
			}
		}

	for(int i=1;i<=n;++i)
		for(int j=1;j<=m;++j)
		{
			bool ok=false;
			for(int k=0;k<4;++k)
			{
				int x=i+dx[k];
				int y=j+dy[k];
				if(!check(x,y))ok=true;
				else adj[i][j].push_back({{x,y},1});
			}
			if(ok)
			{
				wall[i][j]=1;
				q.push({i,j});
			}
		}	

	bfs();

	for(int i=1;i<=n;++i)
		for(int j=1;j<=n;++j)
		{
			if(g[i][j]!='#')continue;
			right(i,j+1);
			left(i,j-1);
			up(i-1,j);
			down(i+1,j);
		}
	for(int i=1;i<=n;++i)
	{
		right(i,1);
		left(i,n);
	}
	for(int j=1;j<=m;++j)
	{
		down(1,j);
		up(m,j);
	}

	dijkstra(sx,sy);
	printf("%d\n",dist[ex][ey]);
	return 0;
}

Compilation message (stderr)

portals.cpp:1:0: warning: ignoring #pragma optimize  [-Wunknown-pragmas]
 #pragma optimize("O3")
 ^
portals.cpp: In function 'void dijkstra(int, int)':
portals.cpp:51:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<adj[x][y].size();++i)
                ^
portals.cpp: In function 'int main()':
portals.cpp:114:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d",&n,&m);
                     ^
portals.cpp:172:8: warning: 'ey' may be used uninitialized in this function [-Wmaybe-uninitialized]
  printf("%d\n",dist[ex][ey]);
        ^
portals.cpp:172:8: warning: 'ex' may be used uninitialized in this function [-Wmaybe-uninitialized]
portals.cpp:171:17: warning: 'sy' may be used uninitialized in this function [-Wmaybe-uninitialized]
  dijkstra(sx,sy);
                 ^
portals.cpp:171:17: warning: 'sx' may be used uninitialized in this function [-Wmaybe-uninitialized]

• Subtask 1: 11 / 11
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 19 / 19
• Subtask 5: 0 / 30