[HDU] 4528 小明系列故事——捉迷藏 -又一个需要靠多维变量来记录一个状态访问没有被访问的广搜题

题目链接：

http://acm.hdu.edu.cn/showproblem.php?pid=4528

方法：地图输入接收完成后，扫面数组，把所有可以看到D和E的位置都标记了，d表示可以看到D，e表示可以看到E,b表示两个都可以看到，这一步放在广搜前的初始化里面。在广搜时，树中的每一个状态节点有3个信息，图中坐标x y，到当前有没有已经看到D getD，到当前有没有已经看到E getE,和当前使用的时间。探寻到一个状态节点，将不将其放入优先队列，从不从该节点开始广搜判断的依据为改状态所处位子是不是墙或D或E（题目要求不能穿过D或E）已经该状态有没有搜索过。判断一个状态有没有搜索过，主要由一个4维变量来记录其访问情况，即用v[x][y][getD][getE]来表示。

除此之外，由于题目要求有时间限制，所以可以用当前使用的时间来剪枝。

感想：重点在于模拟。

代码：

View Code

#include <iostream>
#include <queue>
using namespace std;
int n,m,timeLimit;
int Dx,Dy,Ex,Ey,Sx,Sy;
char map[102][102];
bool v[102][102][2][2];
char start = 'S';
char D ='D';
char E ='E';
char canGetD = 'd';
char canGetE = 'e';
char canGetBoth='b';
char wall = 'X';
char road = '.';
int deriction[4][2]={{0,1},{1,0},{0,-1},{-1,0}};
struct Location
{
int x,y;
int time;
bool getD;
bool getE;
};
struct cmp
{
bool operator()(Location x,Location y)
{
if(x.time>y.time)
return true;
return false;
}
};
bool canGo(int x,int y,bool canGetD,bool canGetE)
{
return map[x][y]!=wall && map[x][y]!=D && map[x][y]!=E && !v[x][y][canGetD][canGetE];
}
void initialize()
{
int t_x=Dx,t_y=Dy;
while(map[t_x+1][t_y]!=wall && map[t_x+1][t_y]!=E)
{
if(map[t_x+1][t_y]==road || map[t_x+1][t_y]==start)
map[t_x+1][t_y] =canGetD;
else
map[t_x+1][t_y] = canGetBoth;
t_x++;
}
t_x=Dx,t_y=Dy;
while(map[t_x-1][t_y]!=wall && map[t_x-1][t_y]!=E)
{
if(map[t_x-1][t_y]==road || map[t_x-1][t_y]==start)
map[t_x-1][t_y] = canGetD;
else
map[t_x-1][t_y] = canGetBoth;
t_x--;
}
t_x=Dx,t_y=Dy;
while(map[t_x][t_y+1]!=wall && map[t_x][t_y+1]!=E)
{
if(map[t_x][t_y+1]==road || map[t_x][t_y+1]==start)
map[t_x][t_y+1] = canGetD;
else
map[t_x][t_y+1] = canGetBoth;
t_y++;
}
t_x=Dx,t_y=Dy;
while(map[t_x][t_y-1]!=wall && map[t_x][t_y-1]!=E)
{
if(map[t_x][t_y-1]==road || map[t_x][t_y-1]==start)
map[t_x][t_y-1] = canGetD;
else
map[t_x][t_y-1] = canGetBoth;
t_y--;
}

t_x=Ex,t_y=Ey;
while(map[t_x+1][t_y]!=wall && map[t_x+1][t_y]!=D)
{
if(map[t_x+1][t_y]==road || map[t_x+1][t_y]==start)
map[t_x+1][t_y] = canGetE;
else
map[t_x+1][t_y] = canGetBoth;
t_x++;
}
t_x=Ex,t_y=Ey;
while(map[t_x-1][t_y]!=wall  &&map[t_x-1][t_y]!=D )
{
if(map[t_x-1][t_y]==road || map[t_x-1][t_y]==start)
map[t_x-1][t_y] = canGetE;
else
map[t_x-1][t_y] = canGetBoth;
t_x--;
}
t_x=Ex,t_y=Ey;
while(map[t_x][t_y+1]!=wall  &&map[t_x][t_y+1]!=D )
{
if(map[t_x][t_y+1]==road || map[t_x][t_y+1]==start)
map[t_x][t_y+1] = canGetE;
else
map[t_x][t_y+1] = canGetBoth;
t_y++;
}
t_x=Ex,t_y=Ey;
while(map[t_x][t_y-1]!=wall  && map[t_x][t_y-1]!=D )
{
if(map[t_x][t_y-1]==road || map[t_x][t_y-1]==start)
map[t_x][t_y-1] = canGetE;
else
map[t_x][t_y-1] = canGetBoth;
t_y--;
}
}
int BFSearch()
{
initialize();
Location startLocation;
startLocation.x = Sx;
startLocation.y = Sy;
startLocation.time = 0;
startLocation.getD = map[startLocation.x][startLocation.y] ==canGetD ||map[startLocation.x][startLocation.y] == canGetBoth;
startLocation.getE = map[startLocation.x][startLocation.y] ==canGetE ||map[startLocation.x][startLocation.y] == canGetBoth;
priority_queue<Location,vector<Location>,cmp> q;
q.push(startLocation);
while(!q.empty())
{
Location t_location = q.top();
q.pop();
if(t_location.getD && t_location.getE)
return t_location.time;
else
{
if(!v[t_location.x][t_location.y][t_location.getD][t_location.getE])
{
v[t_location.x][t_location.y][t_location.getD][t_location.getE]= true;
int n_x,n_y;
bool n_getD,n_getE;
Location n_location;
for(int i=0;i<4;i++)
{
n_x = t_location.x + deriction[i][0];
n_y = t_location.y + deriction[i][1];
n_getD = map[n_x][n_y] ==canGetD || t_location.getD|| map[n_x][n_y] == canGetBoth;
n_getE = map[n_x][n_y] ==canGetE || t_location.getE|| map[n_x][n_y] == canGetBoth;
if(canGo(n_x,n_y,n_getD,n_getE) && t_location.time+1<=timeLimit)
{
n_location.x = n_x;
n_location.y = n_y;
n_location.time = t_location.time+1;
n_location.getD = n_getD;
n_location.getE =n_getE;
q.push(n_location);
}
}
}
}
}
return -1;
}

void main()
{
int tc=0,t;
scanf("%d",&t);
while(tc<t)
{
memset(map,'X',sizeof(map));
memset(v,false,sizeof(v));
scanf("%*c %d %d %d",&n,&m,&timeLimit);
for(int i=1;i<=n;i++)
for(int j=1;j<=m;j++)
{
cin>>map[i][j];
if(map[i][j] ==D)
{
Dx = i;
Dy = j;
}
if(map[i][j] == E)
{
Ex = i;
Ey = j;
}
if(map[i][j] ==start)
{
Sx = i;
Sy = j;
}
}
cout<<"Case "<<tc+1<<":"<<endl<<BFSearch()<<endl;
tc++;
}
}