package Maths; import java.util.*; class KeithNumber { //user-defined function that checks if the given number is Keith or not static boolean isKeith(int x) { //List stores all the digits of the X ArrayList terms=new ArrayList(); //n denotes the number of digits int temp = x, n = 0; //executes until the condition becomes false while (temp > 0) { //determines the last digit of the number and add it to the List terms.add(temp%10); //removes the last digit temp = temp/10; //increments the number of digits (n) by 1 n++; } //reverse the List Collections.reverse(terms); int next_term = 0, i = n; //finds next term for the series //loop executes until the condition returns true while (next_term < x) { next_term = 0; //next term is the sum of previous n terms (it depends on number of digits the number has) for (int j=1; j<=n; j++) next_term = next_term + terms.get(i-j); terms.add(next_term); i++; } //when the control comes out of the while loop, there will be two conditions: //either next_term will be equal to x or greater than x //if equal, the given number is Keith, else not return (next_term == x); } //driver code public static void main(String[] args) { Scanner in = new Scanner(System.in); int n = in.nextInt(); if (isKeith(n)) System.out.println("Yes, the given number is a Keith number."); else System.out.println("No, the given number is not a Keith number."); } }