题目链接：
http://lightoj.com/volume_showproblem.php?problem=1066
题目很容易，广搜和深搜应该都行，我个人认为要注意的是‘A’-->‘ . ’
AC代码：
1 #include <iostream> 2 #include<cstdio> 3 #include<queue> 4 #include <cstring> 5 using namespace std; 6 char s[20][20],ch[50]; 7 int t,n,fine,starex,starey,sum,flag; 8 struct node 9 { 10 int x,y,f; 11 }; 12 int main() 13 { 14 struct node que[2005]; 15 int book[20][20]; 16 int a[4]={1,-1,0,0},b[4]={0,0,1,-1}; 17 int head,tail,tx,ty; 18 strcpy(ch,"ABCDEFGHIJKLMNOPQRSTUVWXYZ"); 19 while(~scanf("%d",&t)) 20 { 21 for(int v=1;v<=t;v++) 22 { 23 scanf("%d",&n); 24 for(int i=0;i<n;i++) 25 scanf("%s",s[i]); 26 fine=0; 27 for(int i=0;i<n;i++) 28 { 29 for(int j=0;j<n;j++) 30 { 31 if(s[i][j]>='A'&&s[i][j]<='Z') 32 { 33 fine=max(s[i][j]-'A',fine); 34 if(s[i][j]=='A') 35 { 36 starex=i;starey=j; 37 s[i][j]='.'; 38 } 39 } 40 } 41 } 42 flag=0;sum=0; 43 head=1;tail=1; 44 memset(que,0,sizeof(que)); 45 que[tail].x=starex;que[tail].y=starey; 46 que[tail].f=0;tail++; 47 memset(book,0,sizeof(book)); 48 book[starex][starey]=1; 49 while(head<tail) 50 { 51 for(int k=0;k<4;k++) 52 { 53 tx=que[head].x+a[k]; 54 ty=que[head].y+b[k]; 55 if(tx<0||tx>=n||ty<0||ty>=n) 56 continue; 57 if((s[tx][ty]=='.'||s[tx][ty]==ch[flag+1])&&book[tx][ty]==0) 58 { 59 book[tx][ty]=1; 60 que[tail].x=tx; 61 que[tail].y=ty; 62 que[tail].f=que[head].f+1; 63 tail++; 64 } 65 if(s[tx][ty]==ch[flag+1]) 66 { 67 s[tx][ty]='.'; 68 flag++; 69 sum=sum+que[tail-1].f; 70 head=0;tail=1; 71 memset(que,0,sizeof(que)); 72 que[tail].x=tx;que[tail].y=ty; 73 que[tail].f=0; 74 memset(book,0,sizeof(book)); 75 book[tx][ty]=1; 76 tail++; 77 break; 78 } 79 } 80 if(flag==fine) 81 break; 82 head++; 83 } 84 printf("Case %d: ",v); 85 if(flag==fine) 86 printf("%d ",sum); 87 else 88 printf("Impossible "); 89 } 90 } 91 return 0; 92 }