Explicitly handle first digit and call recursive function findNDigitNumsUtil for remaining indexes . Note that the first digit is considered to be present in even position .
for ( $ i = 1 ; $ i <= 9 ; $ i ++ ) { $ out [ $ index ] = $ i + '0' ; findNDigitNumsUtil ( $ n , $ out , $ index + 1 , $ evenSum + $ i , $ oddSum ) ; } }