# Is it right that "You may assume that there will be only one unique solution. "??

• My code found correct answer but it was reject because it is different from expected answer
Input:["..9748...","7........",".2.1.9...","..7...24.",".64.1.59.",".98...3..","...8.3.2.","........6","...2759.."]
Output:["139748652","712456839","325169478","987631245","864312597","498527361","576893124","253984716","641275983"]
Expected:["519748632","783652419","426139875","357986241","264317598","198524367","975863124","832491756","641275983"]
and below is my code.

``````class Solution {
private:
int b[9];
int v[9];
int h[9];
vector<vector<char>> board;
vector<pair<int, int>> path;
void built()
{
for (int i = 0; i < 9; i++)b[i] = 1 << i;
for (int i = 0; i < 9; i++)
{
v[i] = 0xFFFFFE00;
h[i] = 0xFFFFFE00;
}
for (int i = 0; i < 9; i++)
{
for (int j = 0; j < 9; j++)
{
char& c = board[i][j];
if (c == '.')path.push_back(make_pair(i, j));
else
{
c = toi(c) - 1;
v[j] |= b[c];
h[i] |= b[c];
}

}
}
for (int i = 0; i < 9; i++)
{
v[i] = ~v[i];
h[i] = ~h[i];
}
}

inline int toi(char c)
{
return c - '0';
}

void set(int i, int j, int bit)
{
board[i][j] = log2(bit);
v[j] ^= bit;
h[i] ^= bit;
}
void unset(int i, int j, int bit)
{
board[i][j] = '.';
v[j] |= bit;
h[i] |= bit;
}

bool dfs(int idx)
{
if (path.size() == idx)return true;
int i = path[idx].first;
int j = path[idx].second;
int intersection = v[j] & h[i];
while (intersection)
{
int bit = intersection & (~intersection + 1);
set(i, j, bit);
if (dfs(idx + 1))return true;
unset(i, j, bit);
intersection ^= bit;
}
return false;
}

public:
void solveSudoku(vector<vector<char>>& b)
{
board = b;
built();
dfs(0);
for (int i = 0; i < 9; i++)
for (int j = 0; j < 9; j++)
b[i][j] = board[i][j] + '1';
}
};
``````

• Your output appears to have

``````139
712
325
``````

for the top-left square, which is invalid, for one reason, because it contains two ones.

I checked this using my solution to the valid sudoku question . Hope this helps!

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