非常简单的一道搜索题，用状态压缩加DP写了一上午，写道后面越来越感觉这题状态压缩没有什么优势，每一行都与前面的行的排列有关系，因此不能够记忆化，没算完一次要把状态清空，可惜到最后还是错了。干脆直接暴力搜索。就这样过了。

代码如下：

#include 
     
      #include 
      
       #include 
       
        #include 
        
         using namespace std;int N, K, hash_x[10], hash_y[10], ans;char G[10][10];void dfs(int x, int y, int k){    if (k == 0) {        ++ans;    }    for (int i = x+1; i <= N; ++i) {        for (int j = 1; j <= N; ++j) {            if (!hash_x[i] && !hash_y[j] && G[i][j] == '#') {                hash_x[i] = 1, hash_y[j] = 1;                dfs(i, j, k-1);                hash_x[i] = hash_y[j] = 0;            }        }    }}int main(){    while (scanf("%d %d", &N, &K), N!=-1||K!=-1) {        ans = 0;        memset(hash_x, 0, sizeof (hash_x));        memset(hash_y, 0, sizeof (hash_y));        for (int i = 1; i <= N; ++i) {            scanf("%s", G[i]+1);        }         for (int i = 1; i <= N; ++i) {            for (int j = 1; j <= N; ++j) {                if (G[i][j] == '#') {                    hash_x[i] = 1, hash_y[j] =1;                    dfs(i, j, K-1);                    hash_x[i] = hash_y[j] = 0;                }            }        }        printf("%d\n", ans);    }}/*8 4.##.###...##...#....##..#...##..#....#.###...##..##...#.#..#...##.#.#..2907*/