leetcode刷题，总结，记录，备忘 36

leetcode36Valid Sudoku

Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.

The Sudoku board could be partially filled, where empty cells are filled with the character '.'.

A partially filled sudoku which is valid.

Note:
A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.

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分别划定3个包含9个set的数组，为9行9列和9个9宫格，然后利用set的特性，不允许重复的元素，进行插入元素判断是否为有效的数独即可，使用i/3*3 + j/3这个公式来判断第i行和第j列的元素属于第几个9宫格，还是很简单的。详情看代码

class Solution {public:    bool isValidSudoku(vector<vector<char>>& board) {        vector<set<char> > vsr(9, set<char>());        vector<set<char> > vsc(9, set<char>());        vector<set<char> > vsm(9, set<char>());                for (int i = 0; i < board.size(); ++i)        {            for (int j = 0; j < board[i].size(); ++j)            {                char val = board[i][j];                if (val == '.')                {                    continue;                }                else                {                    pair<set<char>::iterator, bool> br = vsr[i].insert(val);                    pair<set<char>::iterator, bool> bc = vsc[j].insert(val);                    pair<set<char>::iterator, bool> bm = vsm[i/3*3 + j/3].insert(val);                                        if (!br.second || !bc.second || !bm.second)                    {                        return false;                    }                }            }        }                return true;            }};