我正在尝试为soduko板实现递归回溯解决方案,但是,我得到的板有一个不正确的解决方案。我不确定为什么我的复发是正确的:
bool solveSudoku(vector< vector<char> >& board) {
for (int i=0; i<9; ++i){
for (int j=0; j<9; ++j){
if (board[i][j]=='.'){
for (int k=0; k<9; ++k){
board[i][j]=('1'+k);
if (check(i,j, board) && solveSudoku(board)){
return true;
}
}
return false;
}
}
}
return true;
}
bool check(int i, int j, vector< vector<char> >& board){
//check horizontal
for (int l=0; l<9; ++l){
if (board[i][l]==board[i][j] && l!=j){
return false;
}
}
//check vertical
for (int l=0; l<9; ++l){
if (board[l][j]==board[i][j] && l!=i){
return false;
}
}
//check block
int block_x = i/3;
int block_y = j/3;
block_x*=3;
block_y*=3;
for(int l=0; l<3; ++l){
for (int k=0; k<3; ++k){
if (board[block_x+l][block_y+k]==board[i][j] && block_x+l!=i && block_y+k!=j){
return false;
}
}
}
//all valid so return true
return true;
}
答案 0 :(得分:1)
我最终搞清楚了。我只需要添加board [i] [j] ='。'在返回假之前!这是完整的代码:
bool solveSudoku(vector< vector<char> >& board) {
for (int i=0; i<9; ++i){
for (int j=0; j<9; ++j){
if (board[i][j]=='.'){
for (int k=0; k<9; ++k){
board[i][j]=('1'+k);
if (check(i,j, board) && solveSudoku(board)){
return true;
}
}
board[i][j]='.';
return false;
}
}
}
return true;
}
bool check(int i, int j, vector< vector<char> >& board){
//check horizontal
for (int l=0; l<9; ++l){
if (board[i][l]==board[i][j] && l!=j){
return false;
}
}
//check vertical
for (int l=0; l<9; ++l){
if (board[l][j]==board[i][j] && l!=i){
return false;
}
}
//check block
int block_x = i/3;
int block_y = j/3;
block_x*=3;
block_y*=3;
for(int l=0; l<3; ++l){
for (int k=0; k<3; ++k){
if (board[block_x+l][block_y+k]==board[i][j] && block_x+l!=i && block_y+k!=j){
return false;
}
}
}
//all valid so return true
return true;
}