poj 2312(bfs+priority_queue)

开始的时候想的是bfs。对于每个砖头step+2,然后wa了。看了discuss明白了。这样的话就相当于别的方向只走了一步，而砖头的这个方向是两步，不符合搜索的公平性。

然后把queue换成priority_queue就ac了。

数据：

8 10

YEEEEEBBBB

BBBEEEEEEE

BBBBBBEEEE

BBBBREEEEE

EEEEEEBBBB

BBBBBBBEEE

EEEEEEEEEE

BBBBBEEEET

17



10 10

YEEEEEBBBB

BBBEEEEEEE

BBBBBBEEEE

RRRRBBBBBE

BBEERSSSEE

BBBBREEEEE

EEEEEEBBBB

BBBBBBBEEE

EEEEEEEEEE

BBBBBEEEET

19

 

View Code

 1 // File Name: 2312.cpp

 2 // Author: Missa

 3 // Created Time: 2013/2/19 星期二 11:56:37

 4 

 5 #include<iostream>

 6 #include<cstdio>

 7 #include<cstring>

 8 #include<algorithm>

 9 #include<cmath>

10 #include<queue>

11 #include<stack>

12 #include<string>

13 #include<vector>

14 #include<cstdlib>

15 #include<map>

16 #include<set>

17 using namespace std;

18 #define CL(x,v) memset(x,v,sizeof(x));

19 const int dir[4][2]={-1,0,1,0,0,-1,0,1};

20 const int maxn = 305;

21 int n,m;

22 struct Point

23 {

24     int x,y;

25     int step;

26     Point(){}

27     Point(int x,int y,int step):x(x),y(y),step(step){}

28     bool operator <(const Point&a)const

29     {

30         return step>a.step;

31     }

32 };

33 char g[maxn][maxn];

34 bool vis[maxn][maxn];

35 int bfs(Point st)

36 {

37     priority_queue<Point>q;

38     while(!q.empty()) q.pop();

39     vis[st.x][st.y]=1;

40     q.push(st);

41     while(!q.empty())

42     {

43         Point cur=q.top();q.pop();

44         //cout<<cur.x<<" "<<cur.y<<endl; 

45         if(g[cur.x][cur.y]=='T') return cur.step;

46         for(int i=0;i<4;i++ )

47         {

48             Point nt;

49             nt.x=cur.x+dir[i][0];

50             nt.y=cur.y+dir[i][1];

51             nt.step=cur.step+1;

52             if(nt.x<=0 || nt.y<=0 || nt.x>n || nt.y>m) continue;

53             if(vis[nt.x][nt.y] || g[nt.x][nt.y]=='S' || g[nt.x][nt.y]=='R') continue;

54             if(g[nt.x][nt.y]=='B') nt.step++;

55             vis[nt.x][nt.y]=1;

56             q.push(nt);

57         }

58     }

59     return -1;

60 }

61 int main()

62 {

63     while(~scanf("%d%d",&n,&m))

64     {

65         if(!n && !m) break;

66         CL(g,0);

67         CL(vis,0);

68         for(int i=1;i<=n;i++)

69             scanf("%s",g[i]+1);

70         bool flag=0;

71         for(int i=1;i<=n;i++)

72         {

73             for(int j=1;j<=m;j++)

74             {

75                 if(g[i][j]=='Y')

76                 {

77                     printf("%d\n",bfs(Point(i,j,0)));

78                     flag=1;

79                     break;

80                 }

81             }

82             if(flag) break;

83         }

84     }

85     return 0;

86 }