## POJ3076 Sudoku

• The title is 16*16 GongGe
• See code for pruning
``` #include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;
const int N=;
#define res register int
int map[N][N];
unsigned short t[N][N];
//table[i,j]( Binary system ) Express (i,j) The number you can fill in ,0 Can be filled ,1 Can't fill in
int filled();
inline void my_fill(int x,int y,int a)//(x,y) fill a
{
filled++;
map[x][y]=a;
t[x][y] |=<<(a-);
for(res i= ; i< ; i++)
t[x][i] |=<<(a-),
t[i][y] |=<<(a-);
int r=x/*,c=y/*;//(r,c) Express (x,y) Where 16 The upper left corner of the grid ,( from (0,0) Start )
for(res i= ; i< ; i++)
for(res j= ; j< ; j++) t[r+i][j+c] |=<<(a-);
}
// Judge x in 0 Is there only 1 individual
int count_zero(unsigned short x)
{
int p(-);
for(int i=;x;i++)
{
if(x&==)
{
if(p!=-) return -;
p=i;
}
x>>=;
}
return p;
}
// The first x That's ok , Numbers k+1, return >0 Is the only one that can be filled in k+1 The location of ,-1 It means that there are multiple positions that can be filled or have been filled ,-2 It can't be filled in
inline int col(int x,int k)
{
int p(-);
for(res y= ; y< ; y++)
{
if(map[x][y]==k+) return -;// It has been filled in
if(map[x][y]>) continue;
if((t[x][y]&(<<k))==)
{
if(p!=-) return -;// Multiple occurrences
p=y;
}
}
if(p!=-) return p;
return -;
}
// The first y Column , Numbers k
inline int row(int y,int k)
{
int p=-;
for(res x= ; x< ; x++)
{
if(map[x][y]==k+) return -;
if(map[x][y]>) continue;
if((t[x][y]&(<<k))==)
{
if(p!=-) return -;
p=x;
}
}
if(p!=-) return p;
return -;
}
inline void grid(int r,int c,int k,int &x,int &y)
// With (r,c) It's in the upper left corner 16 GongGe , Numbers k+1,(x,y) Is the only fillable coordinate [
{
x=-;
for(res i= ; i< ; i++)
for(res j= ; j< ; j++)
{
if(map[r+i][c+j]==k+) {x=-; return ;}
if(map[r+i][c+j]>) continue;
if((t[r+i][c+j]&(<<k))==)
{
if(x!=-) {x=-; return ;}
x=i,y=j;
}
}
}
inline int count_1(unsigned short x) {
int tmp();
while(x) {
if(x&) tmp++;
x>>=;
}
return tmp;
}
bool search()
{
if(filled==) return true;
// Let's see if there is a certain grid
for(res x= ; x< ; x++)
for(res y= ; y< ; y++)
{
if(map[x][y]>) continue;
int k=count_zero(t[x][y]);
if(k!=-) my_fill(x,y,k+);
}
for(res x= ; x< ; x++)
for(res k= ; k< ; k++)
{
int y=col(x,k);
if(y==-) return false;
if(y!=-) my_fill(x,y,k+);
}
for(res y= ; y< ; y++)
for(res k= ; k< ; k++)
{
int x=row(y,k);
if(x==-) return false;
if(x!=-) my_fill(x,y,k+);
}
for(res r= ; r< ; r+=)
for(res c= ; c< ; c+=)
for(res k= ; k< ; k++)
{
int x,y;
grid(r,c,k,x,y);
if(x==-) return false;
if(x!=-) my_fill(r+x,c+y,k+);
}
if(filled==) return true;
int t_filled(filled);
int t_map[N][N];
unsigned short t_t[N][N];
for(res i= ; i< ; i++)
for(res j= ; j< ; j++)
t_map[i][j]=map[i][j],
t_t[i][j]=t[i][j];
// Find the least possible grid to enumerate
int mx,my,mn=;
for(res i= ; i< ; i++)
for(res j= ; j< ; j++)
{
if(map[i][j]>) continue;
int r=-count_1(t[i][j]);
// Undetermined
if(r<mn)
{
mn=r; mx=i; my=j;
}
}
for(res k= ; k< ; k++)
if((t[mx][my]&<<k)==)
{
my_fill(mx,my,k+);
if(search()) return true;
filled=t_filled;
for(res i= ; i< ; i++)
for(res j= ; j< ; j++)
map[i][j]=t_map[i][j],
t[i][j]=t_t[i][j];
}
return false;
}
char ar[N];
int main()
{
while()
{
filled=;
memset(map,,sizeof(map)); memset(t,,sizeof(t));
for(int i= ; i< ; i++)
{
if(scanf("%s",ar)==EOF) return ;
for(int j= ; j< ; j++)
if(ar[j]!='-') my_fill(i,j,ar[j]-'A'+);
}
search();
for(res i= ; i< ; i++)
{
for(res j= ; j< ; j++) printf("%c",map[i][j]+'A'-);
puts("");
}
puts("");
}
return ;
}```

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