LEARNING JOURNAL

function isValidSudoku(board: string[][]): boolean {
    const rowChecks: Record<string, boolean>[] = Array(9).fill(0).map(_ => new Object() as Record<string, boolean>);
    const colChecks: Record<string, boolean>[] = Array(9).fill(0).map(_ => new Object() as Record<string, boolean>);
    const squareChecks: Record<string, boolean>[] = Array(9).fill(0).map(_ => new Object() as Record<string, boolean>);

    for(let row = 0; row < board.length; row++){

        for(let col = 0; col < board[0].length; col++) {
            const curNum = board[row][col];
            
            if(curNum === ".") continue;
            
            if(rowChecks[row][curNum]) {
                return false
            }
            else rowChecks[row][curNum] = true;
            
            if(colChecks[col][curNum]) return false;
            else colChecks[col][curNum] = true

            const squareI = Math.floor(col/3) + Math.floor(row/3)*3;
            if(squareChecks[squareI][curNum]) return false;
            else squareChecks[squareI][curNum] = true;

        }
    }

    return true;
};