多个目标点的最短路径

#include<iostream>
#include<cstring>
#include<queue>
using namespace std;
char map[205][205];
int count[205][205];
int a[205][205],b[205][205];
int m,n;
const int w=1e7;
int u[4][2]={1,0,-1,0,0,1,0,-1};
struct node{
    int x,y;
    int step;
};
int bfs(int x,int y,int e[205][205])
{
    memset(count,0,sizeof(count));
    queue<node>f;
    node now;
    now.x=x;
    now.y=y;
    now.step=0;
    f.push(now);
    count[x][y]=1;
    while(!f.empty())
    {
        now=f.front();
        f.pop();
        for(int i=0;i<4;i++)
        {
            int dx=now.x+u[i][0];
            int dy=now.y+u[i][1];
            if(count[dx][dy]==0&&dx>=1&&dx<=m&&y>=1&&y<=n&&map[dx][dy]!='#')
            {
                node next;
                next.x=dx;
                next.y=dy;
                count[next.x][next.y]=1;
                e[dx][dy]=now.step+1;
                next.step=now.step+1;
                f.push(next);
            }
        }
    }
}
int main()
{
    int s,k1,k2,h1,h2,d1,d2,min,k;
    while(cin>>m>>n)
    {
        min=w;
        for(int i=1;i<=m;i++)
        cin>>(map[i]+1);
        s=1;
        for(int i=1;i<=m;i++)
            for(int j=1;j<=n;j++)
            {
                    if(map[i][j]=='Y')
                       {
                           k1=i;h1=j;
                       }
                    else
                    if(map[i][j]=='M')
                    {
                        k2=i;h2=j;
                    }
            }
            memset(a,0,sizeof(a));
            memset(b,0,sizeof(b));
            d1=bfs(k1,h1,a);
            d2=bfs(k2,h2,b);
            for(int i=1;i<=m;i++)
                for(int j=1;j<=n;j++)
                {
                    if(map[i][j]=='@')
                    {
                        k=a[i][j]+b[i][j];
                        if(k<min)
                        min=k;
                    }
                }
        cout<<min*11<<endl;
    }
}