leetcode36

【题目】

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.

即判断当前的数独空是否是合法的，不需考虑是否有解

【思路】

一行，或者一列的情况都比较好取到对应的数值，那么关键问题是，怎么在i和j的值在0-9之间变化的时候，将行列的值映射到九宫格的位置上，经过数学分析，可以得到当：

i = 0:1:8，j = 0:1:8时 ，九宫格对应的行列数为[3*(i/3)+j/3][3*(i%3)+j%3]

【Java代码】

class Solution {    public boolean isValidSudoku(char[][] board) {        Map<Integer,Integer> judge_row = new HashMap<Integer,Integer>();Map<Integer,Integer> judge_col = new HashMap<Integer,Integer>();Map<Integer,Integer> judge_squ = new HashMap<Integer,Integer>();for(int i = 0 ; i < 9 ; i++){judge_row.clear();judge_col.clear();judge_squ.clear();for(int j = 0 ; j < 9 ; j++){char curr_row = board[i][j];char curr_col = board[j][i];char curr_squ = board[3*(i/3)+j/3][3*(i%3)+j%3];if(curr_row != '.' & judge_row.containsKey(Integer.valueOf(curr_row)))return false;if(curr_col != '.' & judge_col.containsKey(Integer.valueOf(curr_col)))return false;if(curr_squ != '.' & judge_squ.containsKey(Integer.valueOf(curr_squ)))return false;judge_row.put(Integer.valueOf(curr_row), 1);judge_col.put(Integer.valueOf(curr_col), 1);judge_squ.put(Integer.valueOf(curr_squ), 1);}}return true;    }}