POJ 3074 Sudoku (Dacing Links)

推荐一个写数独很好的博客：http://www.cnblogs.com/grenet/p/3163550.html

主要是把九宫格里的元素换到矩阵里面再求解dancing links

网上找的一模版

 #include<cstdio>
 #include<cstring>
 #define MAXM 10
 #define MAXL 324
 #define MAXN 240000
 #define INF 0x7FFFFFFF
 char sd[MAXM][MAXM];
 int L[MAXN], R[MAXN], U[MAXN], D[MAXN], H[MAXN];
 int size, C[MAXN], S[MAXN], X[MAXN], Q[MAXN], vis[MAXL * ];
 bool Read()
 {
     int i, j;
     for (i = ; i < MAXM; i++)
     {
         for (j = ; j < MAXM; j++)
         {
             scanf(" %c", &sd[i][j]);
             if (sd[i][j] == 'e')
                 return false;
         }
     }
     return true;
 }
 void Init()
 {
     int i;
     for (i = ; i <= MAXL; i++)
     {
         L[i + ] = i;
         R[i] = i + ;
         U[i] = D[i] = i;
         S[i] = ;
     }
     R[MAXL] = ;
     size = MAXL + ;
 }
 void Remove(int c)
 {
     int i, j;
     L[R[c]] = L[c];
     R[L[c]] = R[c];
     for (i = D[c]; i != c; i = D[i])
     {
         for (j = R[i]; j != i; j = R[j])
         {
             U[D[j]] = U[j];
             D[U[j]] = D[j];
             S[C[j]]--;
         }
     }
 }
 void Resume(int c)
 {
     int i, j;
     L[R[c]] = c;
     R[L[c]] = c;
     for (i = D[c]; i != c; i = D[i])
     {
         for (j = R[i]; j != i; j = R[j])
         {
             U[D[j]] = j;
             D[U[j]] = j;
             S[C[j]]++;
         }
     }
 }
 inline void Link(int r, int c)
 {
     D[size] = D[c];
     U[size] = c;
     U[D[c]] = size;
     D[c] = size;
     if (H[r] < )
         H[r] = L[size] = R[size] = size;
     else
     {
         L[size] = H[r];
         R[size] = R[H[r]];
         L[R[H[r]]] = size;
         R[H[r]] = size;
     }
     S[c]++;
     X[size] = r;
     C[size++] = c;
 }
 bool Dance(int now)
 {
     int i, j, c, temp;
     if (R[] == )
         return true;
     for (temp = INF,i = R[]; i; i = R[i])
     {
         if (S[i] < temp)
         {
             temp = S[i];
             c = i;
         }
     }
     Remove(c);
     for (i = D[c]; i != c; i = D[i])
     {
         vis[X[i]] = true;
         for (j = R[i]; j != i; j = R[j])
             Remove(C[j]);
         if (Dance(now + ))
             return true;
         for (j = L[i]; j != i; j = L[j])
             Resume(C[j]);
         vis[X[i]] = false;
     }
     Resume(c);
     return false;
 }
 int main()
 {
     int i, j, k, r;
     while (Read())
     {
         Init();
         for (r = , i = ; i < MAXM; i++)
         {
             for (j = ; j < MAXM; j++)
             {
                 if (sd[i][j] == '.')
                 {
                     for (k = ; k < MAXM; k++)
                     {
                         H[++r] = -;
                         Q[r] = k;
                         Link(r, (i - ) *  + k);
                         Link(r,  + (j - ) *  + k);
                         Link(r,  + ((i - ) /  *  + (j - ) / ) *  + k);
                         Link(r,  + (i - ) *  + j);
                     }
                 }
                 else
                 {
                     H[++r] = -;
                     k = sd[i][j] - '';
                     Q[r] = k;
                     Link(r, (i - ) *  + k);
                     Link(r,  + (j - ) *  + k);
                     Link(r,  + ((i - ) /  *  + (j - ) / ) *  + k);
                     Link(r,  + (i - ) *  + j);
                 }
             }
         }
         memset(vis, false, sizeof(vis));
         Dance();
         for (i = ; i <= r; i++)
         {
             if (vis[i])
                 printf("%d", Q[i]);
         }
         putchar('\n');
     }
     return ;
 }