Run a loop from 1 to N . Check if previous number is single digit or not . If yes then product = 1 else take modulus . Then again check if previous number is single digit or not if yes then store previous number , else store its first value Then for every i store value in the array .
for ( int i = 1 ; i <= N ; i ++ ) { product = a [ i - 1 ] / 10 ; if ( product == 0 ) product = 1 ; else product = a [ i - 1 ] % 10 ; int val = a [ i - 1 ] / 10 ; if ( val == 0 ) val = a [ i - 1 ] ; a [ i ] = a [ i - 1 ] + ( val * product ) ; }