題目傳送門
判斷一個 9x9 的數獨是否有效。隻需要根據以下規則,驗證已經填入的數字是否有效即可。
數字 1-9 在每一行隻能出現一次。
數字 1-9 在每一列隻能出現一次。
數字 1-9 在每一個以粗實線分隔的 3x3 宮内隻能出現一次。
上圖是一個部分填充的有效的數獨。
數獨部分空格内已填入了數字,空白格用 ‘.’ 表示。
示例 1:
輸入:
[
[“5”,“3”,".",".",“7”,".",".",".","."],
[“6”,".",".",“1”,“9”,“5”,".",".","."],
[".",“9”,“8”,".",".",".",".",“6”,"."],
[“8”,".",".",".",“6”,".",".",".",“3”],
[“4”,".",".",“8”,".",“3”,".",".",“1”],
[“7”,".",".",".",“2”,".",".",".",“6”],
[".",“6”,".",".",".",".",“2”,“8”,"."],
[".",".",".",“4”,“1”,“9”,".",".",“5”],
[".",".",".",".",“8”,".",".",“7”,“9”]
]
輸出: true
示例 2:
輸入:
[
[“8”,“3”,".",".",“7”,".",".",".","."],
[“6”,".",".",“1”,“9”,“5”,".",".","."],
[".",“9”,“8”,".",".",".",".",“6”,"."],
[“8”,".",".",".",“6”,".",".",".",“3”],
[“4”,".",".",“8”,".",“3”,".",".",“1”],
[“7”,".",".",".",“2”,".",".",".",“6”],
[".",“6”,".",".",".",".",“2”,“8”,"."],
[".",".",".",“4”,“1”,“9”,".",".",“5”],
[".",".",".",".",“8”,".",".",“7”,“9”]
]
輸出: false
解釋: 除了第一行的第一個數字從 5 改為 8 以外,空格内其他數字均與 示例1 相同。
但由于位于左上角的 3x3 宮内有兩個 8 存在, 是以這個數獨是無效的。
說明:
一個有效的數獨(部分已被填充)不一定是可解的。
隻需要根據以上規則,驗證已經填入的數字是否有效即可。
給定數獨序列隻包含數字 1-9 和字元 ‘.’ 。
給定數獨永遠是 9x9 形式的。
思路:按照題目要求,一行不能有同樣的數字,一列不能有同樣的數字,3*3小方格也不能有相同的數字。是以我們可以用一個二維布爾變量數組a[i][j],表示目前行或者列中j有沒有出現過,結果為true時說明不符合數獨規則,輸出false,如果為false時說明j第一次在本行或者列出現,将a[i][j]設為true,繼續判斷。
class Solution {
public:
bool isValidSudoku(vector<vector<char>>& board) {
if(board.size()==0) return false;
else
{
vector<vector<bool>> row(9,vector<bool>(9,false));
vector<vector<bool>> col(9,vector<bool>(9,false));
vector<vector<bool>> cell(9,vector<bool>(9,false));
for(int i=0;i<9;i++)
for(int j=0;j<9;j++)
{
if(board[i][j]>='0'&&board[i][j]<='9')
{
int num=board[i][j]-'1';
if(row[i][num]||col[num][j]||cell[3*(i/3)+j/3][num])//小的3*3子產品依次從左到右從上到下編号
return false;
row[i][num]=true;
col[num][j]=true;
cell[3*(i/3)+j/3][num]=true;
}
}
return true;
}
}
};