FZU Problem 1491 机器人测试(BFS)

#include<iostream>
#include<cstdio>
#include<queue>
#include<conio.h>
#include<cstring>
using namespace std;
int map[1002][1002];
int vis[1002][1002];
int val[1000001];
int N,Num,Max;
int dir[][2] = {-1,0,0,1,1,0,0,-1};
struct Point
{
int x,y;
int flag;
};
bool Check(int x,int y,int F)
{
if( x < 0 || x >= N || y < 0 || y >= N)
return 1;
if( F && vis[x][y] )
return 1;
if(map[x][y] == -2 )
return 1;
if( F && map[x][y] == -3 )
return 1;
return 0;
}
void BFS(int x,int y,int F)
{
queue<Point> Que;
Point P,Q;
P.x = x; P.y = y; P.flag = F;
Que.push(P);
if(F){
val[Num] = map[x][y];
if(map[x][y] == -1)
val[Num] += 1;
vis[x][y] = Num;
}
while( !Que.empty()){
P = Que.front();
Que.pop();
for(int i=0; i<4; i++){
Q.x = P.x + dir[i][0];
Q.y = P.y + dir[i][1];
Q.flag = P.flag;
if(P.flag){
if( !Check(Q.x,Q.y,1) )//不出界、未遍历过、不是-2、-3
{
val[Num] += map[Q.x][Q.y];//该水池的值
if(map[Q.x][Q.y] == -1)
val[Num] += 1;//经过则起点加一
vis[Q.x][Q.y] = Num;//标记第几个水池
Que.push(Q);//入队
}
}
else{
if( !Check(Q.x,Q.y,0) )//不是-2、墙时
{
if( vis[Q.x][Q.y] && val[vis[Q.x][Q.y]] > Max )
Max = val[vis[Q.x][Q.y]];
map[Q.x][Q.y] = -2;//把走过的路变为墙
Que.push(Q);
}
}
}
}
}
int main()
{
int i,j;
int start_x,start_y;
while(~scanf("%d",&N))
{
for(i=0; i<N; i++)
for(j=0; j<N; j++){
scanf("%d",&map[i][j]);
if(map[i][j] == -1){
start_x = i;
start_y = j;
}
}
Num = 0;
memset(vis,0,sizeof(vis));
memset(val,0,sizeof(val));
for(i=0; i<N; i++)
for(j=0; j<N; j++){
if( !vis[i][j] && map[i][j] != -2 && map[i][j] != -3    ){
Num++;
BFS(i,j,1);
}
}
Max = 0;
BFS(start_x,start_y,0);
cout<<Max<<endl;
}
return 0;
}