【LeetCode 37】解数独
【题解】
回溯法搞一下。 用set和数组下标判重。【代码】
class Solution {
public:
set<int> myset[9];
int hang[9][10],lie[9][10];
bool dfs(vector<vector<char>>& board,int x,int y){
if (y==9){
x++;y = 0;
}
if (x==9){
return true;
}
if (board[x][y]!='.'){
return dfs(board,x,y+1);
}
for (int i = 1;i <= 9;i++){
if (hang[x][i] || lie[y][i]) continue;
int idx = (x/3)*3+y/3;
if (myset[idx].find(i)!=myset[idx].end()) continue;
hang[x][i] = lie[y][i] = 1;
myset[idx].insert(i);
char key = i+'0';
board[x][y] = key;
if (dfs(board,x,y+1)) return true;
board[x][y] = '.';
hang[x][i] = lie[y][i] = 0;
myset[idx].erase(i);
}
return false;
}
void solveSudoku(vector<vector<char>>& board) {
for (int i = 0;i < 9;i++) myset[i].clear();
memset(hang,0,sizeof hang);memset(lie,0,sizeof lie);
for (int i = 0 ;i < 9;i++)
for (int j = 0;j < 9;j++)
if (board[i][j]!='.'){
int x = board[i][j]-'0';
hang[i][x]=1;
lie[j][x] = 1;
int ti = i/3,tj = j/3;
int idx = ti*3+tj;
myset[idx].insert(x);
}
dfs(board,0,0);
}
};