博文中会简要介绍Leetcode P0036题目分析及解题思路。
“Valid Sudoku”属于“看图看题说话”的风格。按照题目中的要求写出判断公式即可。这里可以不用HashTable来记录数字出现个数，这样可以减少时间开销。
Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:
- Each row must contain the digits 1-9 without repetition.
- Each column must contain the digits 1-9 without repetition.
- Each of the 9 3x3 sub-boxes of the grid must contain the digits 1-9 without repetition.
以下是Java的题解代码实现。
class Solution {
public boolean isValidSudoku(char[][] board) {
int[][][] digitCounterForSubbox = new int[3][3][10];
int[][] digitCounterForRow = new int[9][10];
int[][] digitCounterForCol = new int[9][10];
for (int row=0; row<9; ++row) {
for (int col=0; col<9; ++col) {
if (board[row][col] == '.')
continue;
int digit = board[row][col]-'0';
++digitCounterForRow[row][digit];
++digitCounterForCol[col][digit];
++digitCounterForSubbox[row/3][col/3][digit];
if (digitCounterForRow[row][digit] > 1
|| digitCounterForCol[col][digit] > 1
|| digitCounterForSubbox[row/3][col/3][digit] > 1) {
return false;
}
}
}
return true;
}
}