Algorithm/sudoku/main.cc

#include <cstdio>
#include <cstring>
using namespace std;

#define mx 100100
int sum = 0;
int arr[10][10];
inline int read() {
  char c = getchar();
  if (c == '.')
    c = '0';
  while (c < '0' || c > '9') {
    c = getchar();
    if (c == '.')
      c = '0';
  }
  return c - '0';
}
struct dancing_link {
  int n, m, cnt;
  int l[mx], r[mx], u[mx], d[mx], row[mx], col[mx];
  int h[mx];
  int s[mx];
  int ansk[mx];
  void init(int _n, int _m) {
    n = _n, m = _m;
    int i;
    for (i = 0; i <= m; i++) {
      r[i] = i + 1;
      l[i] = i - 1;
      u[i] = d[i] = i;
    }
    r[m] = 0;
    l[0] = m;
    memset(h, -1, sizeof(h));
    memset(s, 0, sizeof(s));
    cnt = m + 1;
  }
  void link(int R, int C) {
    s[C]++;
    row[cnt] = R;
    col[cnt] = C;
    u[cnt] = C;
    d[cnt] = d[C];
    u[d[C]] = cnt;
    d[C] = cnt;
    if (h[R] < 0)
      h[R] = r[cnt] = l[cnt] = cnt;
    else {
      r[cnt] = h[R];
      l[cnt] = l[h[R]];
      r[l[h[R]]] = cnt;
      l[h[R]] = cnt;
    }
    cnt++;
  }
  void remove(int c) {
    r[l[c]] = r[c], l[r[c]] = l[c];
    for (int i = d[c]; i != c; i = d[i]) {
      for (int j = r[i]; j != i; j = r[j]) {
        u[d[j]] = u[j];
        d[u[j]] = d[j];
        s[col[j]]--;
      }
    }
  }
  void resume(int c) {
    for (int i = u[c]; i != c; i = u[i]) {
      for (int j = l[i]; j != i; j = l[j]) {
        u[d[j]] = j;
        d[u[j]] = j;
        s[col[j]]++;
      }
    }
    r[l[c]] = c;
    l[r[c]] = c;
  }
  bool dance(int deep) {
    if (r[0] == 0) {
      int x, y, v;
      for (int i = 0; i < deep; i++) {
        x = (ansk[i] - 1) / 9 / 9;
        y = (ansk[i] - 1) / 9 % 9;
        v = (ansk[i]) % 9;
        if (v == 0)
          v = 9;
          arr[x][y] = v;
      }
      return 1;
    }
    int c = r[0];
    for (int i = r[0]; i != 0; i = r[i])
      if (s[i] < s[c])
        c = i;
    remove(c);
    for (int i = d[c]; i != c; i = d[i]) {
      ansk[deep] = row[i];
      for (int j = r[i]; j != i; j = r[j])
        remove(col[j]);
      if (dance(deep + 1) == 1)
        return 1;
      for (int j = l[i]; j != i; j = l[j])
        resume(col[j]);
    }
    resume(c);
    return false;
  }
} dlx;
int main() {
  dlx.init(729, 324);
  int x;
  int o;
  for (int i = 0; i <= 8; i++) {
    for (int j = 0; j <= 8; j++) {
        arr[i][j] = x = read();
      for (int k = 1; k <= 9; k++) {
        if (x != k && x != 0)
          continue;
        o = i * 9 * 9 + j * 9 + k;
        dlx.link(o, i * 9 + j + 1);
        dlx.link(o, i * 9 + 81 + k);
        dlx.link(o, j * 9 + 81 * 2 + k);
        dlx.link(o, 81 * 3 + (i / 3 * 3 + j / 3) * 9 + k);
      }
    }
  }
  dlx.dance(0);
  for (int i = 0; i <= 8; i++) {
    for (int j = 0; j <= 8; j++)
      printf("%d", arr[i][j]);
    printf("\n");
  }
  return 0;
}