Returns count of numbers with k as last digit .
public static int counLastDigitK ( int low , int high , int k ) { int mlow = 10 * ( int ) Math . ceil ( low / 10.0 ) ; int mhigh = 10 * ( int ) Math . floor ( high / 10.0 ) ; int count = ( mhigh - mlow ) / 10 ; if ( high % 10 >= k ) count ++ ; if ( low % 10 <= k && ( low % 10 ) > 0 ) count ++ ; return count ; }