狀態壓縮+寬搜
#include<cstdio>
#include<iostream>
#include<cstring>
#include<queue>
using namespace std;
int n,m,t;
int sx,sy;
int vis[25][25][1<<12];
char map[25][25];
int dir[4][2]={1,0,-1,0,0,1,0,-1};
struct state
{
int x,y,key,nowTime;
state(){}
state(int xx,int yy,int kk,int nn):x(xx),y(yy),key(kk),nowTime(nn){}
void get(int xx,int yy,int kk,int nn)
{
x=xx,y=yy,key=kk,nowTime=nn;
}
bool judge()
{
if(x>=0&&x<n&&y>=0&&y<m&&map[x][y]!='*')
return 1;
return 0;
}
}start;
int bfs()
{
queue<state> q;
q.push(start);
while(!q.empty())
{
state u=q.front();
q.pop();
if(map[u.x][u.y]=='^'&&u.nowTime<t)
return u.nowTime;
if(u.nowTime>=t) break;
for(int i=0;i<4;i++)
{
state v=u;
v.x+=dir[i][0] ;
v.y+=dir[i][1] ;
v.nowTime++ ;
if(v.judge())
{
if(map[v.x][v.y]>='A'&&map[v.x][v.y]<='J')
{
int key=(map[v.x][v.y]-'A');
if((v.key&(1<<key))&&!vis[v.x][v.y][v.key])
{
vis[v.x][v.y][v.key]=1;
q.push(v) ;
}
}
else if(map[v.x][v.y]>='a'&&map[v.x][v.y]<='j')
{
int key =(1<<(map[v.x][v.y] - 'a')) ;
v.key = (v.key|key) ;
if(!vis[v.x][v.y][v.key])
{
vis[v.x][v.y][v.key]=1;
q.push(v);
}
}
else
{
if(!vis[v.x][v.y][v.key])
{
vis[v.x][v.y][v.key]=1;
q.push(v);
}
}
}
}
}
return -1;
}
int main()
{
while(cin>>n>>m>>t)
{
memset(vis,0,sizeof(vis));
for(int i=0;i<n;i++)
{
cin>>map[i];
for(int j=0;j<m;j++)
if(map[i][j]=='@')
{
start.get(i,j,0,0);
vis[i][j][0]=1;
}
}
cout<<bfs()<<endl;
}
return 0;
}