hdu1198 Farm Irrigation —— dfs or 并查集

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

dfs：

 #include<cstdio>//hdu1198 dfs
 #include<cstring>

 int well[][] = { {,,,,},{,,,,},{,,,,},{,,,,},{,,,,},{,,,,},{,,,,},{,,,,},{,,,,},{,,,,},{,,,,}};

 const int ca[][] = {,,,,,,,,,}, mov[][] = {,,-,,,,,-};
 int m,n,sum, map[][],id[][];

 void build(int set, int x, int y)
 {
     for(int k = ; k<; k++)
     {
         if(well[set][k])
         {
             map[*x+ca[k][]][*y+ca[k][]] = ;
         }
     }
 }

 void dfs(int x, int y, int iden)
 {
     id[x][y] = iden;
     for(int i = ; i<; i++)
     {
         int xx = x + mov[i][], yy = y + mov[i][];
         if(xx< || xx>*m- || yy< || yy>*n- ) continue;
         if(map[xx][yy] && !id[xx][yy])
         dfs(xx,yy,iden);
     }
 }

 int main()
 {
     char init[];
     while(scanf("%d%d",&m,&n) && (m!=- || n!=- ))
     {
         memset(map,,sizeof(map));
         memset(id,,sizeof(id));
         for(int i = ; i<m; i++)
         {
             scanf("%s",init);
             for(int j = ; j<n; j++)
             build(init[j]-,i,j);
         }
         sum = ;
         for(int i = ; i<=*m-; i++)
         {

             for(int j = ; j<=*n-; j++)
             {
                 //printf("%d ",map[i][j]);
                 if(map[i][j] && !id[i][j])
                 {
                     dfs(i,j,++sum);
                 }
             }
             //putchar('\n');
         }

         printf("%d\n",sum);

     }
     return ;
 }

并查集：

 #include<cstdio>//hdu1198 并查集 每个格子的标号为i*n+j，初始father也为i*n+j，以次来作为合并集合的依据
 #include<cstring>

 int n,m,father[][];
 char map[][];
 char type[][]={"","","","","","",
                "","","","",""};

 int find(int x)
 {
     return (x==father[x/n][x%n])?x:find(father[x/n][x%n]);
 }

 int unit(int a, int b)
 {
     a = find(a);
     b = find(b);
     if(a!=b)//合并集合
         father[a/n][a%n] = b;
 }

 int judge(int i, int j)
 {   //判断是否与左边相连
     if(j> && type[map[i][j]-'A'][]=='' && type[map[i][j-]-'A'][]=='')
         unit(i*n+j,i*n+j-);
     //判断是否与上边相连
     if(i> && type[map[i][j]-'A'][]=='' && type[map[i-][j]-'A'][]=='')
         unit(i*n+j,(i-)*n+j);
 }

 int main()
 {
     while(scanf("%d%d",&m,&n) && (m!=- || n!=-))
     {
         for(int i = ; i<m; i++)
         {
             scanf("%s",&map[i]);
             for(int j = ; j<n; j++)
             {   //初始化为自己
                 father[i][j] = i*n+j;
             }
         }

         //并查集过程
         for(int i = ; i<m; i++)
         for(int j = ; j<n; j++)
         judge(i,j);

         int sum = ;
         for(int i = ; i<m; i++)
         for(int j = ; j<n; j++)//看看有多少个“根节点”
             if(father[i][j]==i*n+j) sum++;

         printf("%d\n",sum);
     }

 }