[Matrix][Medium] 36. Valid Sudoku

https://leetcode.com/problems/valid-sudoku/description

 

Q. 유효한 sudoku인지 판단하라. 

 

 

Solution

 위 3 조건을 체크하는 로직을 만든다. 

 

 다양한 방법이 있을 수 있다고 본다. 

 

 최대한 간단하게 만들어 본다.

 

bool IsValid(char ch, HashSet<char> cache)
{
    if(ch<'0' || ch>'9') 
        return false;
    if(cache.Contains(ch))
        return false;
    return true;
}
public bool IsValidSudoku(char[][] board) 
{
    // Row check.
    for(int y = 0; y < board.Length; ++y)
    {
        HashSet<char> buff = new HashSet<char>();
        for(int x = 0; x < board[0].Length; ++x)
        {
            char cur = board[y][x];
            if(cur == '.')  continue;
            if(!IsValid(cur, buff)) 
                return false;
            buff.Add(board[y][x]);
        }
    }

    // Col check.
    for(int x = 0; x < board[0].Length; ++x)
    {
        HashSet<char> buff = new HashSet<char>();
        for(int y = 0; y < board.Length; ++y)
        {
            char cur = board[y][x];
            if(cur == '.')  continue;
            if(!IsValid(cur, buff)) 
                return false;
            buff.Add(board[y][x]);
        }
    }

    // 3x3 box check.
    for(int iY = 0; iY < 9; iY += 3)
    {
        for(int iX = 0; iX < 9; iX += 3)
        {
            HashSet<char> buff = new HashSet<char>();
            for(int y = 0; y < 3; ++y)
            {
                for(int x = 0; x < 3; ++x)
                {
                    char cur = board[y+iY][x+iX];
                    if(cur == '.')  continue;
                    // Console.WriteLine(cur);
                    if(!IsValid(cur, buff))     
                        return false;
                    buff.Add(cur);
                }
            }
            Console.WriteLine("");
        }
    }
    return true;
}

 

결과.