HDU ACM 1198 Farm Irrigation(BFS)

http://acm.hdu.edu.cn/showproblem.php?pid=1198

题意:输入A~K 各代表一个图形,判断有多少个联通分支

听说用DFS比较简单,但是还是用了BFS

定义一个函数 way() 判断向四个方向是否联通

BFS中用四句if语句(可优化)判断当前位置能不能走到下一个位置 和 下个位置能不能走到当前位置

View Code 
  1 #include <iostream>
  2 #include <queue>
  3 using namespace std;
  4 struct Node
  5 {
  6     int x;
  7     int y;
  8 };
  9 char map[55][55];
 10 int used[55][55];
 11 
 12 bool way(int x,int y,int w)
 13 {
 14     if(w == 0 && (map[x][y] == 'A' || map[x][y] == 'B' || map[x][y] == 'E' 
 15         || map[x][y] == 'G' || map[x][y] == 'H' || map[x][y] == 'J' || map[x][y] == 'K' ))
 16     {
 17         return 1;
 18     }
 19     if(w == 1 && (map[x][y] == 'C' || map[x][y] == 'D' || map[x][y] == 'E' 
 20         || map[x][y] == 'H' || map[x][y] == 'I' || map[x][y] == 'J' || map[x][y] == 'K' ))
 21     {
 22         return 1;
 23     }
 24     if(w == 2 && (map[x][y] == 'A' || map[x][y] == 'C' || map[x][y] == 'F' 
 25         || map[x][y] == 'G' || map[x][y] == 'H' || map[x][y] == 'I' ||  map[x][y] == 'K' ))
 26     {
 27         return 1;
 28     }
 29     if(w == 3 && (map[x][y] == 'B' || map[x][y] == 'D' || map[x][y] == 'F' 
 30         || map[x][y] == 'G' || map[x][y] == 'I' || map[x][y] == 'J' || map[x][y] == 'K' ))
 31     {
 32         return 1;
 33     }
 34     return 0;
 35 }
 36 int BFS(int x,int y)
 37 {
 38     memset(used,0,sizeof(used));
 39     queue <Node> q;
 40     int i,j;
 41     Node a,b,c;
 42     int sum =0;
 43     while(1)
 44     {
 45         
 46         int mark = 0;
 47         for(i=0;i<x;i++)
 48         {
 49             for(j=0;j<y;j++)
 50             {
 51                 if(!used[i][j])
 52                 {
 53                     mark = 1;
 54                     a.x = i;
 55                     a.y = j;
 56                     q.push(a);
 57                     used[a.x][a.y] = 1;
 58                     break;
 59                 }
 60             }
 61             if(mark == 1)
 62             {
 63                 break;
 64             }
 65         }
 66         
 67         if(mark == 0)
 68         {
 69             return sum;
 70         }
 71         sum++;
 72         while(!q.empty())
 73         {
 74             b=q.front();
 75             q.pop();
 76 
 77             c.x = b.x + -1;
 78             c.y = b.y + 0;
 79             if(way(b.x,b.y,0) && way(c.x,c.y,1) && c.x>=0 && c.y>=0 && c.x<x && c.y<y && !used[c.x][c.y])
 80             {
 81                 q.push(c);
 82                 used[c.x][c.y] = 1;
 83             }
 84 
 85             c.x = b.x + 1;
 86             c.y = b.y + 0;
 87             if(way(b.x,b.y,1) && way(c.x,c.y,0) && c.x>=0 && c.y>=0 && c.x<x && c.y<y && !used[c.x][c.y])
 88             {
 89                 q.push(c);
 90                 used[c.x][c.y] = 1;
 91             }
 92 
 93             c.x = b.x + 0;
 94             c.y = b.y + -1;
 95             if(way(b.x,b.y,2) && way(c.x,c.y,3) && c.x>=0 && c.y>=0 && c.x<x && c.y<y && !used[c.x][c.y])
 96             {
 97                 q.push(c);
 98                 used[c.x][c.y] = 1;
 99             }
100 
101             c.x = b.x + 0;
102             c.y = b.y + 1;
103             if(way(b.x,b.y,3) && way(c.x,c.y,2) && c.x>=0 && c.y>=0 && c.x<x && c.y<y && !used[c.x][c.y])
104             {
105                 q.push(c);
106                 used[c.x][c.y] = 1;
107             }
108         }
109     }
110     return -1;
111 }
112 int main()
113 {
114     
115     int x,y;
116     while(cin>>x>>y)
117     {
118         memset(map,0,sizeof(map));
119         if(x == -1 && y == -1)
120         {
121             return 0;
122         }
123         int i,j;
124         for(i=0;i<x;i++)
125         {
126             for(j=0;j<y;j++)
127             {
128                 cin>>map[i][j];
129             }
130         }
131         cout<<BFS(x,y)<<endl;
132     }
133     return 0;
134 }

 

posted @ 2012-08-23 20:48  zx雄  阅读(189)  评论(0)  编辑  收藏  举报