【HDOJ】1045 Fire Net

经典深搜。注意满足条件。

 #include <stdio.h>
 #include <string.h>

 #define MAXNUM 5

 char map[MAXNUM][MAXNUM];
 int visit[MAXNUM][MAXNUM];

 int chk(int row, int col, int n) {
     int i, k;

     if (row< || row>=n || col< || col>=n )
         return ;
     if (visit[row][col] || map[row][col]!='.')
         return ;

     // if this position is valid or not
     k = ;
     for (i=col-; i>=; --i) {
         if (map[row][i] == 'X')
             break;
         if (map[row][i] == '.' && visit[row][i]) {
             k = ;
             break;
         }
     }
     if (k) return ;

     for (i=col+; i<n; ++i) {
         if (map[row][i] == 'X')
             break;
         if (map[row][i] == '.' && visit[row][i]) {
             k = ;
             break;
         }
     }
     if (k) return ;

     for (i=row-; i>=; --i) {
         if (map[i][col] == 'X')
             break;
         if (map[i][col] == '.' && visit[i][col]) {
             k = ;
             break;
         }
     }
     if (k) return ;

     for (i=row+; i<n; ++i) {
         if (map[i][col] == 'X')
             break;
         if (map[i][col] == '.' && visit[i][col]) {
             k = ;
             break;
         }
     }

     if (k)
         return ;
     else
         return ;
 }

 int dfs(int n) {
     int i, j, tmp, max = ;

     for (i=; i<n; ++i) {
         for (j=; j<n; ++j) {
             if ( chk(i, j, n) ) {
                 visit[i][j] = ;
                 tmp = dfs(n) + ;
                 if (tmp > max)
                     max = tmp;
                 visit[i][j] = ;
             }
         }
     }

     return max;
 }

 int main() {
     int n, amount;
     int i;

     while (scanf("%d", &n)!=EOF && n) {
         getchar();
         for (i=; i<n; ++i)
             gets(map[i]);

         memset(visit, , sizeof(visit));
         amount = dfs(n);
         printf("%d\n", amount);
     }

     return ;
 }