diff --git a/sudoku/main.cc b/sudoku/main.cc
new file mode 100644
index 0000000..dedb9ef
--- /dev/null
+++ b/sudoku/main.cc
@@ -0,0 +1,134 @@
+#include <cstdio>
+#include <cstring>
+using namespace std;
+
+#define mx 100100
+int sum = 0;
+int a[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;
+        a[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++) {
+      a[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", a[i][j]);
+    printf("\n");
+  }
+  return 0;
+}