My first attempt at validating a Sukoku board. (Also my first introduction to Sudoku at all!)

validSudoku.leetcode.go

// https://leetcode.com/problems/valid-sudoku/submissions/900490403/

func isValidSudoku(board [][]byte) bool {
    // 9 spaces is > 8 bits so we use 2 bytes (an int16)
    rowsMap := [9]int16{}
    colsMap := [9]int16{}
    gridMap := [9]int16{}

    for row:=0; row<9; row++ {
        for col:=0; col<9; col++ {
            if board[row][col] == 46 {
                continue
            }

            // ASCII 48 == 0
            val := board[row][col] - 48
            gridIndex := col/3 + (row/3) * 3

            // We set bits on/off instead of using a map with 1-2 bytes per answer stored
            var flag int16 = 1<<val
            if rowsMap[row]&flag == flag || colsMap[col]&flag == flag || gridMap[gridIndex]&flag == flag {
                return false
            } 
            rowsMap[row] |= flag
            colsMap[col] |= flag    
            gridMap[gridIndex] |= flag
        }
    }
    return true
}