Counts the number of 2 s in a number at d - th digit
< ? php function count2sinRangeAtDigit ( $ number , $ d ) { $ powerOf10 = ( int ) pow ( 10 , $ d ) ; $ nextPowerOf10 = $ powerOf10 * 10 ; $ right = $ number % $ powerOf10 ; $ roundDown = $ number - $ number % $ nextPowerOf10 ; $ roundup = $ roundDown + $ nextPowerOf10 ; $ digit = ( $ number / $ powerOf10 ) % 10 ;