Floodfill (DIJKSTRA)

#include <iostream>
#include <vector>
#include <queue>
#define INF (1<<29)
using namespace std;

int dx[] = {0, 0, 1,-1};
int dy[] = {1,-1, 0, 0};

struct grafo {
    vector< string > ady;
    vector<vector<int>> dist;
    priority_queue< pair<int, pair<int,int> > > pq;
    int n, m, p;

    void leer ()
    {
        cin>>n>>m;

        ady.resize(n);
        dist = vector< vector<int> > (n, vector<int> (m, INF) );

        for(int x=0; x<n; x++)
            for(int y=0; y<m; y++)
                cin>>ady[x][y];
        cin>>p;
    }

    bool visitable (int x, int y)
    {
        if ((0<=x && x<n) && (0<=y && y<m))
            if(ady[x][y]!='#')
                return true;
        return false;
    }

    void iniciar (int x, int y)
    {
        if ( visitable( x,y ) )
        {
            dist[x][y] = ady[x][y]-'0';
            pq.push( {ady[x][y], {x,y} } );
        }
    }

    void dijkstra ()
    {
        for(int x=0; x<n; x++)
        {
            iniciar(x, 0  );
            iniciar(x, m-1);
        }
        for(int y=0; y<m; y++)
        {
            iniciar(0  , y);
            iniciar(n-1, y);
        }

        while( pq.size() )
        {
            int x = pq.top().second.first;
            int y = pq.top().second.second;
            pq.pop();

            for(int i=0; i<4; i++)
            {
                int vx = x+dx[i];
                int vy = y+dy[i];
                int costo = ady[vx][vy]-'0';

                if ( visitable(vx,vy) )
                {
                    if ( dist[x][y]+costo < dist[vx][vy] )
                    {
                        dist[vx][vy] = dist[x][y]+costo;
                        pq.push( {-dist[vx][vy], {vx,vy} } );
                    }
                }
            }
        }

        /**for(int x=0; x<n; x++)
        {
            for(int y=0; y<m; y++)
                cout<<ady[x][y]<<"  ";
            cout<<endl;
        }
        cout<<endl;*/

        for(int x=0; x<n; x++)
        {
            for(int y=0; y<m; y++)
            {
                if (ady[x][y]=='#')
                    cout<<"#  ";
                else if (dist[x][y]==INF)
                    cout<<"N0 ";
                else if (dist[x][y]<10)
                    cout<<dist[x][y]<<"  ";
                else cout<<dist[x][y]<<" ";
            }
            cout<<endl;
        }
        cout<<endl;

        int x, y;
        for(int i=0; i<p; i++)
        {
            cin>>x>>y;
            cout<<x<<" "<<y<<" -> ";
            if(dist[x-1][y-1]==INF)
                cout<<"NO"<<endl;
            else cout<<dist[x-1][y-1]<<endl;
        }
    }
};

int main()
{
    grafo g;
    g.leer();
    g.dijkstra();

    return 0;
}

/*

8 15
0 # # # # # # # # # # # # # #
1 1 6 8 8 8 8 # 1 8 8 8 2 2 #
# 1 # # # # # # 1 # # # # 2 #
# 1 2 2 2 2 0 8 1 2 2 2 2 2 #
# 1 # # # # 0 # 1 # # # # # #
# 1 # # 5 # 0 1 1 # 9 9 # 1 #
# 3 3 # 5 # # # # # 9 # # 1 #
# # # # 5 # # # # # 9 # # # #
4
7 3
4 8
2 13
7 13

*/