gistfile1.scala

package proj_euler

/*
 * A palindromic number reads the same both ways.
 *  The largest palindrome made from the product of two 2-digit numbers is 9009 = 91  99.
 *  
 *  Find the largest palindrome made from the product of two 3-digit numbers.
 */

//906609

object Problem4 {
	
    def solve()  : Int = {
        // generate seq from 100 to 999
        var r1 = Range(100, 1000).toList
        // generate seq from 100 to 999
        var r2 = Range(100, 1000).toList

        // combine all elements (Int, Int)
        val r3 = r1.map(elem1 => r2.map(elem2 => (elem1, elem2 ))).flatten
        // filter palindrome
        val r4 = r3.filter(elem => 
            is_palin(elem._1 * elem._2) == true)         
        // find max palindrome
        val max = r4.map(elem => elem._1 * elem._2).max
           
        return max
    }
    
    /*
     * check is 'n' palindrome or not  
     */
    def is_palin(n : Int) : Boolean ={
	var p = n.toString.reverse
	if (n.toString == p)
	    return true
	else
	    return false
	}
}