> For the complete documentation index, see [llms.txt](https://aaronice.gitbook.io/lintcode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://aaronice.gitbook.io/lintcode/hash-table/valid-sudoku.md).

# Valid Sudoku

核心要点是如何生成 box index

> One could use `box_index = (row / 3) * 3 + columns / 3` where `/` is an integer division.