Valid Sudoku

Problem

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 '.'.

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Idea

• Each row must have the numbers 1-9 occuring just once.
• Each column must have the numbers 1-9 occuring just once.
• And the numbers 1-9 must occur just once in each of the 9 sub-boxes of the grid.
• 先检查行，再检查列，再检查每个3*3的cube
• 判断是否重复的方法是讲一行或者一列或者1个3*3放入vector中。 然后再存入hash_map中，利用hash_map的find()!=hash_map.end()来判断是否有重复的 复杂度O(n)

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Notes

• How to insert hash map
• How to find an element in the hash_map
• How to push/pop an element by vector

Solution

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