poj--2676 Sudoku(dfs)

题解

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

#define MEM(a, v) memset(a, v, sizeof(a))

const int N = 9;
int a[N+1][N+1];
int rowFlag[N+1][N+1], colFlag[N+1][N+1], squFlag[N+1][N+1];
int t;
string s;

bool Sudoku(int r, int c){
if(r > N) return true;
bool flag = false;
if(a[r][c]){
if(c == N)  flag = Sudoku(r + 1, 1);
else flag = Sudoku(r, c + 1);
return flag;
}

for(int i = 1; i <= N; ++i){
int k = 3*((r-1)/3)+(c-1)/3 + 1;
if(!rowFlag[r][i] && !colFlag[c][i] && !squFlag[k][i]){
rowFlag[r][i] = colFlag[c][i] = squFlag[k][i] = 1;
a[r][c] = i;
if(c == N) flag = Sudoku(r + 1, 1);
else flag = Sudoku(r, c + 1);
if(flag) return true;   // 填数成功不回溯
a[r][c] = 0;
rowFlag[r][i] = colFlag[c][i] = squFlag[k][i] = 0;
}
}
return false;
}

int main(){
#ifdef EXMY
freopen("data.in", "r", stdin);
#endif // EXMY
/// 712K    438MS
cin >> t;
while(t--){
MEM(rowFlag, 0);
MEM(colFlag, 0);
MEM(squFlag, 0);
for(int i = 1; i <= N; ++i){
cin >> s;
for(int j = 1; j <= s.length(); ++j){
int t = s[j-1] - '0';
a[i][j] = t;
if(a[i][j]){
int k = 3*((i-1)/3)+(j-1)/3 + 1;
rowFlag[i][t] = colFlag[j][t] = squFlag[k][t] = 1;
}
}
}
Sudoku(1, 1);
for(int i = 1; i <= N; ++i){
for(int j = 1; j <= N; ++j) cout << a[i][j];
cout << endl;
}
}

return 0;
}

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

#define MEM(a, v) memset(a, v, sizeof(a))

const int N = 9;
int a[N+1][N+1];
int rowFlag[N+1][N+1], colFlag[N+1][N+1];
int squFlag[3][3][N+1];
int t;
string s;

bool Sudoku(int k){
if(k >= N * N) return true;
int r = k / 9;
int c = k % 9;
if(a[r][c]) return Sudoku(k + 1);
for(int i = 1; i <= N; ++i){
if(!rowFlag[r][i] && !colFlag[c][i] && !squFlag[r/3][c/3][i]){
rowFlag[r][i] = colFlag[c][i] = squFlag[r/3][c/3][i] = 1;
a[r][c] = i;
if(Sudoku(k + 1)) return true;
rowFlag[r][i] = colFlag[c][i] = squFlag[r/3][c/3][i] = 0;
a[r][c] = 0;
}
}
return false;
}

int main(){
#ifdef EXMY
freopen("data.in", "r", stdin);
#endif // EXMY

cin >> t;
while(t--){
MEM(rowFlag, 0);
MEM(colFlag, 0);
MEM(squFlag, 0);
for(int i = 0; i < N; ++i){
cin >> s;
for(int j = 0; j < s.length(); ++j){
int t = s[j] - '0';
a[i][j] = t;
if(a[i][j]){
rowFlag[i][t] = colFlag[j][t] = squFlag[i/3][j/3][t] = 1;
}
}
}
Sudoku(0);
for(int i = 0; i < N; ++i){
for(int j = 0; j < N; ++j) cout << a[i][j];
cout << endl;
}
}

}