Valid Sudoku

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描述
Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules
http://sudoku.com.au/TheRules.aspx .
The Sudoku board could be partially filled, where empty cells are filled with the character ‘.’.
这里写图片描述
分析：
必须保证每一行、每一列、每一个九宫格内不出现重复元素。
只要分别检测就可以了。

class Solution {public:bool isValidSudoku(const vector<vector<char>>& board) {bool used[9];for (int i = 0; i < 9; ++i) {fill(used, used + 9, false);for (int j = 0; j < 9; ++j) // 检查行if (!check(board[i][j], used))return false;fill(used, used + 9, false);for (int j = 0; j < 9; ++j) // 检查列if (!check(board[j][i], used))return false;}for (int r = 0; r < 3; ++r) // 检查9 个子格子for (int c = 0; c < 3; ++c) {fill(used, used + 9, false);for (int i = r * 3; i < r * 3 + 3; ++i)for (int j = c * 3; j < c * 3 + 3; ++j)if (!check(board[i][j], used))return false;}return true;}bool check(char ch, bool used[9]) {if (ch == '.') return true;if (used[ch - '1']) return false;return used[ch - '1'] = true;}};

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