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[LeetCode] Valid 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.

 

这题看似很复杂,其实很无脑,因为也无需判断是否是可解的sudoku board。遍历这个board,找到不为空的位置时,分别考察其行,列和3x3;如果出现重复则为非法,遍历完毕全部通过检查则为合法。

    bool isValidSudoku(vector<vector<char> > &board) {            unordered_set<int> column;    unordered_set<int> square;    unordered_set<int> row;         // check for colum    for (int i = 0; i < 9; i++) {        for (int j = 0; j < 9; j++) {            char item = board[j][i];            if (item != ‘.‘) {                int num = atoi(&item);                if (column.find(num) == column.end()){                    column.insert(atoi(&item));                }                else {                    return false;                }            }        }        column.clear();    }    // check for row    for (int i = 0; i < 9; i++) {        for (int j = 0; j < 9; j++) {            char item = board[i][j];            if (item != ‘.‘) {                int num = atoi(&item);                if (row.find(num) == row.end()) {                    row.insert(num);                }                else {                    return false;                }            }        }        row.clear();    }        // check for 3x3    for (int offsetY = 0; offsetY < 3; offsetY++) {        for (int offsetX = 0; offsetX < 3; offsetX++) {                        for (int i = 3*offsetY; i < 3*offsetY+3; i++) {                for (int j = 3*offsetX; j < 3*offsetX+3; j++) {                    char item = board[i][j];                    if (item != ‘.‘) {                        int num = atoi(&item);                        if (square.find(num) == square.end()) {                            square.insert(num);                        }                        else {                            return false;                        }                    }                }            }            square.clear();                    }    }        return true;    }

 

[LeetCode] Valid Sudoku