poj2676 Sudoku（DFS）

做了很久还是参考了别人的答案orz，其实也不难啊。我要开始学一下怎么写搜索了。。。

题目链接：poj2676 Sudoku

题解：暴力搜索，DFS每个空白格子所放数字。

 #include<cstdio>
 #include<iostream>
 #include<cstring>
 #include<algorithm>
 #include<vector>
 using namespace std;
 bool row_f[][];//row_f[i][j]=1表示第i行已经放了数字j
 bool col_f[][];
 bool block_f[][];
 int g[][];
 struct blank{
     int i, j;
     blank(int i, int j):i(i),j(j) {}
 };
 vector<blank> bk;
 int get_blockid(int i, int j){
     i /= ;
     j /= ;
     return i *  + j;
 }
 bool ok(int i, int j, int x){
     return !row_f[i][x] && !col_f[j][x] && !block_f[get_blockid(i, j)][x];
 }
 void setnum(int i, int j, int x, int f){
     row_f[i][x] = f;
     col_f[j][x] = f;
     block_f[get_blockid(i, j)][x] = f;
 }
 bool dfs(int n){//处理前n个空白格
     if(n < ) return true;
     int r = bk[n].i;
     int c = bk[n].j;
     for(int x = ; x <= ; ++x){
         if(ok(r, c, x)){
             setnum(r, c, x, );
             g[r][c] = x;
             if(dfs(n - )) return true;
             setnum(r , c, x, );
         }
     }
     return false;
 }
 int main(){
     int t, i, j;
     char c;
     scanf("%d", &t);
     while(t--){
         bk.clear();
         memset(row_f, , sizeof(row_f));
         memset(col_f, , sizeof(col_f));
         memset(block_f, , sizeof(block_f));
         for(i = ; i < ; ++i){
             for(j =  ;j < ; ++j){
                 cin >> c;
                 g[i][j] = c - '';
                 if(!g[i][j])
                     bk.push_back(blank(i, j));
                 else
                     setnum(i, j, g[i][j], );
             }
         }
         if(dfs(bk.size()-)){
             for(i = ; i < ; ++i){
                 for(j = ; j <  ; ++j)
                     printf("%c", g[i][j] + '');
                 printf("\n");
             }
         }
     }
     return ;
 }