Get bit i for a given number n. (i count from 0 and starts from right)
i是从右边数起的，并从0开始计数。
int getBit(int num, int i){
int result = num & (1<<i) ;
if( result ) {
return 1;
}
else {
return 0 ;
}
// the if-else statement is equal to the statement return ( bool )result ;
}
