HDU1429+bfs+状态压缩

bfs+状态压缩
思路：用2进制表示每个钥匙是否已经被找到。、

  1 /*

  2 bfs+状态压缩

  3 思路：用2进制表示每个钥匙是否已经被找到。

  4 */

  5 #include<algorithm>  

  6 #include<iostream>  

  7 #include<string.h>  

  8 #include<stdlib.h>  

  9 #include<stdio.h>  

 10 #include<math.h>  

 11 #include<queue>  

 12 #include<stack>  

 13 #include<map>  

 14 #include<set>  

 15 using namespace std;  

 16 typedef long long int64;  

 17 //typedef __int64 int64;  

 18 typedef pair<int64,int64> PII;  

 19 #define MP(a,b) make_pair((a),(b))   

 20 const int inf = 0x3f3f3f3f;  

 21 const double pi=acos(-1.0);  

 22 const int dx[]={1,-1,0,0};  

 23 const int dy[]={0,0,1,-1};  

 24 const double eps = 1e-8;  

 25 const int maxm = (1<<10)+5;  

 26 const int maxn = 22;

 27 

 28 bool vis[ maxn ][ maxn ][ maxm ];

 29 char mat[ maxn ][ maxn ];

 30 struct Point {

 31     int x,y,ti,key;

 32 };

 33 Point s,e;

 34 queue<Point>q;

 35 

 36 int bfs( int n,int m,int sumT ){

 37     memset( vis,false,sizeof( vis ) );

 38     while( !q.empty() )

 39         q.pop();

 40     Point cur;

 41     cur = s;

 42     vis[ cur.x ][ cur.y ][ cur.key ] = true;

 43     q.push( cur );

 44     while( !q.empty() ){

 45         cur = q.front();

 46         q.pop();

 47         if( cur.x==e.x && cur.y==e.y  ){

 48             e.ti = min( e.ti,cur.ti );

 49         }

 50         if( cur.ti>=sumT ) continue;

 51         for( int i=0;i<4;i++ ){

 52             Point nxt ;

 53             nxt.x = cur.x + dx[ i ];

 54             nxt.y = cur.y + dy[ i ];

 55             nxt.ti = cur.ti + 1;

 56             nxt.key = cur.key;

 57             if( nxt.x<0||nxt.x>=n||nxt.y<0||nxt.y>=m ) continue;

 58             if( mat[ nxt.x ][ nxt.y ]=='*' ) continue;

 59             if( mat[ nxt.x ][ nxt.y ]>='a' && mat[ nxt.x ][ nxt.y ]<='z' ){

 60                 nxt.key = cur.key|(1<<(mat[ nxt.x ][ nxt.y ]-'a'));

 61             }//there may be a new key

 62             if( vis[ nxt.x ][ nxt.y ][ nxt.key ]==true )

 63                 continue;

 64             vis[ nxt.x ][ nxt.y ][ nxt.key ] = true;

 65             if( mat[ nxt.x ][ nxt.y ]>='A' && mat[ nxt.x ][ nxt.y ]<='Z' ){

 66                 if( nxt.key&(1<<(mat[ nxt.x ][ nxt.y ]-'A')) ){

 67                     q.push( nxt );

 68                 }

 69             }

 70             else 

 71                 q.push( nxt );

 72         }

 73     }

 74     if( e.ti>=sumT )

 75         return -1;

 76     else

 77         return e.ti;

 78 }

 79             

 80 int main(){

 81     int n,m,sumT;

 82     while( scanf("%d%d%d",&n,&m,&sumT)==3 ){

 83         for( int i=0;i<n;i++ ){

 84             scanf("%s",mat[ i ]);

 85             for( int j=0;j<m;j++ ){

 86                 if( mat[ i ][ j ]=='@' ){

 87                     s.x = i;

 88                     s.y = j;

 89                     s.ti = 0;

 90                     s.key = 0;

 91                     mat[ i ][ j ] = '.';

 92                 }

 93                 if( mat[ i ][ j ]=='^' ){

 94                     e.x = i;

 95                     e.y = j;

 96                     e.ti = sumT+1;

 97                     mat[ i ][ j ] = '.';

 98                 }

 99             }

100         }

101         printf("%d\n",bfs( n,m,sumT ));

102     }

103     return 0;

104 }

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