POJ 2676 Sudoku 跳舞链 || dfs

题目：

题意：

思路：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>

using namespace std;

const int X = 100000 + 10, N = 800 + 10, M = 400 + 10, INF = 0x3f3f3f3f;

struct DLX
{
int U[X], D[X], L[X], R[X], row[X], col[X];
int H
, S[M];
int head, sz, tot, n, m, ans
;
void init(int _n, int _m)
{
n = _n, m = _m;
for(int i = 0; i <= m; i++)
L[i] = i-1, R[i] = i+1, U[i] = D[i] = i, S[i] = 0;
head = 0, tot = 0, sz = m;
L[head] = m, R[m] = head;
for(int i = 1; i <= n; i++) H[i] = -1;
}
void link(int r, int c)
{
++S[col[++sz]=c];
row[sz] = r;
D[sz] = D[c], U[D[c]] = sz;
U[sz] = c, D[c] = sz;
if(H[r] < 0) H[r] = L[sz] = R[sz] = sz;
else R[sz] = R[H[r]], L[R[H[r]]] = sz, L[sz] = H[r], R[H[r]] = sz;
}
void del(int c)
{
L[R[c]] = L[c], R[L[c]] = R[c];
for(int i = D[c]; i != c; i = D[i])
for(int j = R[i]; j != i; j = R[j])
D[U[j]] = D[j], U[D[j]] = U[j], --S[col[j]];
}
void recover(int c)
{
for(int i = U[c]; i != c; i = U[i])
for(int j = L[i]; j != i; j = L[j])
D[U[j]] = U[D[j]] = j, ++S[col[j]];
R[L[c]] = L[R[c]] = c;
}
bool dance(int dep)
{
if(R[head] == head)
{
tot = dep-1; return true;
}
int c = R[head];
for(int i = R[head]; i != head; i = R[i])
if(S[i] < S[c]) c = i;
del(c);
for(int i = D[c]; i != c; i = D[i])
{
ans[dep] = row[i];
for(int j = R[i]; j != i; j = R[j]) del(col[j]);
if(dance(dep + 1)) return true;
for(int j = L[i]; j != i; j = L[j]) recover(col[j]);
}
recover(c);
return false;
}
}dlx;
void calc(int x, int y, int k, int len)
{
int r = ((x-1) * len + (y-1)) * len + k;
dlx.link(r, (x-1) * len + k);
dlx.link(r, len*len + (y-1) * len + k);

int base = sqrt(1.0 * len);
int block = (x-1) / base * base + (y-1) / base + 1;
dlx.link(r, len*len*2 + (block-1) * len + k);
dlx.link(r, len*len*3 + (x-1) * len + y);
}
void print(int len)
{
sort(dlx.ans + 1, dlx.ans + 1 + dlx.tot);
for(int i = 1; i <= len; i++)
{
for(int j = 1; j <= len; j++)
printf("%d", dlx.ans[(i-1)*len+j] - ((i-1)*len + (j-1)) * len);
printf("\n");
}
}
int main()
{
int t, len = 9;
scanf("%d", &t);
while(t--)
{
char ch;
dlx.init(len * len * len, len * len * 4);
for(int i = 1; i <= len; i++)
for(int j = 1; j <= len; j++)
{
scanf(" %c", &ch);
if(ch == '0')
for(int k = 1; k <= len; k++) calc(i, j, k, len);
else calc(i, j, ch-'0', len);
}
dlx.dance(1);
print(len);
}
return 0;
}

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

const int N = 10;
char s

;
bool row

, col

, block

;
bool found;
void dfs(int i, int j)
{
if(i == 9 && j == 0)
{
found = true;
for(int i = 0; i < 9; i++)
printf("%s\n", s[i]);
}
if(s[i][j] == '0')
for(int k = 1; k <= 9; k++)
{
if(!row[i][k] && !col[j][k] && !block[i/3*3+j/3+1][k])
{
s[i][j] = k + '0';
row[i][k] = true;
col[j][k] = true;
block[i/3*3+j/3+1][k] = true;
if(j != 8) dfs(i, j + 1);
else dfs(i + 1, 0);
if(found) return;
s[i][j] = '0';
row[i][k] = false;
col[j][k] = false;
block[i/3*3+j/3+1][k] = false;
}
}
else
{
if(j != 8) dfs(i, j + 1);
else dfs(i + 1, 0);
}
}
int main()
{
int t;
scanf("%d", &t);
while(t--)
{
memset(row, 0, sizeof row);
memset(col, 0, sizeof col);
memset(block, 0, sizeof block);
for(int i = 0; i < 9; i++)
scanf("%s", s[i]);
for(int i = 0; i < 9; i++)
for(int j = 0; j < 9; j++)
{
row[i][s[i][j]-'0'] = true;
col[j][s[i][j]-'0'] = true;
block[i/3*3+j/3+1][s[i][j]-'0'] = true;
}
found = false;
dfs(0, 0);
}
return 0;
}