subboxes[i][j][val] 用于存储第 i 行、第 j 列个小九宫格 val + 1 的个数,其中:
i = r / 3,j = c / 3
???????遍历每个小格子,统计数字的个数,分别计入对应的哈希表里,如果个数超过了 1 ,则数独无效
class Solution {
public:
bool isValidSudoku(vector<vector<char>>& board) {
int rows[9][9];
int columns[9][9];
int subboxes[3][3][9];
memset(rows, 0, sizeof(rows));
memset(columns, 0, sizeof(columns));
memset(subboxes, 0, sizeof(subboxes));
for (int i = 0; i < 9; ++i) {
for (int j = 0; j < 9; ++j) {
char c = board[i][j];
if (c != '.') {
int index = c - '0' - 1;
rows[i][index]++;
columns[j][index]++;
subboxes[i / 3][j / 3][index]++;
if (rows[i][index] > 1 ||
columns[j][index] > 1 ||
subboxes[i / 3][j / 3][index] > 1) {
return false;
}
}
}
}
return true;
}
};
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