$/**$

$*$ Check if some number $(1$~$9)$ appears more than once in the array.

$*$

$*$ A possible algorithm:

$*1.$ Create a boolean array of nine elements, each element corresponding to one number.

$*2.$ Loop through the input array arr, if the corresponding position of a number

$*$ in the boolean array is false, mark it as true.

$*3.$ If the position of a number is already true, return false $($duplicate number found$).$

$*$

$*$ @param arr A $1$d array that needs to be checked

$*$ @return true if no conflict; false otherwise, and when arr is null.

$*/$

public static boolean checkConflictForArray$($int$[]$ arr$)\{$

return false;

$\}$