HDU 2602 Find a way BFS搜索

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <string>
#include <cmath>
#include <set>
#include <queue>
#include <cstring>
using namespace std;
typedef long long LL;
const int maxn=200+5;
const int INF=0x3f3f3f3f;
char s[maxn][maxn];
int a[maxn][maxn];
int b[maxn][maxn];
int n,m;
int dx[4]={0,0,-1,1};
int dy[4]={-1,1,0,0};
struct Point
{
int x,y;
Point(){}
Point(int p,int q)
{
x=p,y=q;
}
} o,t;
queue<Point>Y,M;
vector<Point>v;
int main()
{
while(~scanf("%d%d",&n,&m))
{
v.clear();
memset(a,-1,sizeof(a));
memset(b,-1,sizeof(b));
for(int i=1;i<=n;++i)
scanf("%s",s[i]+1);
for(int i=1;i<=n;++i)
{
for(int j=1;j<=m;++j)
{
if(s[i][j]=='@')v.push_back(Point(i,j));
else if(s[i][j]=='Y')Y.push(Point(i,j)),a[i][j]=0;
else if(s[i][j]=='M')M.push(Point(i,j)),b[i][j]=0;
}
}
while(!Y.empty())
{
o=Y.front();
Y.pop();
for(int i=0;i<4;++i)
{
t.x=o.x+dx[i];
t.y=o.y+dy[i];
if(t.x<1||t.x>n||t.y<1||t.y>m)continue;
if(s[t.x][t.y]=='#'||a[t.x][t.y]>=0)continue;
a[t.x][t.y]=a[o.x][o.y]+1;
Y.push(t);
}
}
while(!M.empty())
{
o=M.front();
M.pop();
for(int i=0;i<4;++i)
{
t.x=o.x+dx[i];
t.y=o.y+dy[i];
if(t.x<1||t.x>n||t.y<1||t.y>m)continue;
if(s[t.x][t.y]=='#'||b[t.x][t.y]>=0)continue;
b[t.x][t.y]=b[o.x][o.y]+1;
M.push(t);
}
}
int ans=INF;
for(int i=0;i<v.size();++i)
{
int x=v[i].x,y=v[i].y;
if(a[x][y]==-1||b[x][y]==-1)continue;
ans=min(ans,a[x][y]+b[x][y]);
}
printf("%d\n",ans*11);
}
return 0;
}