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 * 3];
bool Read()
{
    int i, j;
    for (i = 1; i < MAXM; i++)
    {
        for (j = 1; j < MAXM; j++)
        {
            scanf(" %c", &sd[i][j]);
            if (sd[i][j] == 'e')
                return false;
        }
    }
    return true;
}
void Init()
{
    int i;
    for (i = 0; i <= MAXL; i++)
    {
        L[i + 1] = i;
        R[i] = i + 1;
        U[i] = D[i] = i;
        S[i] = 0;
    }
    R[MAXL] = 0;
    size = MAXL + 1;
}
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] < 0)
        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[0] == 0)
        return true;
    for (temp = INF,i = R[0]; 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 + 1))
            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 = 0, i = 1; i < MAXM; i++)
        {
            for (j = 1; j < MAXM; j++)
            {
                if (sd[i][j] == '.')
                {
                    for (k = 1; k < MAXM; k++)
                    {
                        H[++r] = -1;
                        Q[r] = k;
                        Link(r, (i - 1) * 9 + k);
                        Link(r, 81 + (j - 1) * 9 + k);
                        Link(r, 162 + ((i - 1) / 3 * 3 + (j - 1) / 3) * 9 + k);
                        Link(r, 243 + (i - 1) * 9 + j);
                    }
                }
                else
                {
                    H[++r] = -1;
                    k = sd[i][j] - '0';
                    Q[r] = k;
                    Link(r, (i - 1) * 9 + k);
                    Link(r, 81 + (j - 1) * 9 + k);
                    Link(r, 162 + ((i - 1) / 3 * 3 + (j - 1) / 3) * 9 + k);
                    Link(r, 243 + (i - 1) * 9 + j);
                }
            }
        }
        memset(vis, false, sizeof(vis));
        Dance(0);
        for (i = 1; i <= r; i++)
        {
            if (vis[i])
                printf("%d", Q[i]);
        }
        putchar('
');
    }
    return 0;
}