Algorithm/sudoku/main.cc

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#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;
}