KeithNumber.java

packagecom.thealgorithms.maths;

importjava.util.ArrayList;
importjava.util.Collections;
importjava.util.Scanner;

finalclassKeithNumber {
privateKeithNumber() {
 }

// user-defined function that checks if the given number is Keith or not
staticbooleanisKeith(intx) {
// List stores all the digits of the X
ArrayList<Integer> terms = newArrayList<>();
// n denotes the number of digits
inttemp = x;
intn = 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);
intnextTerm = 0;
inti = n;
// finds next term for the series
// loop executes until the condition returns true
while (nextTerm < x) {
nextTerm = 0;
// next term is the sum of previous n terms (it depends on number of digits the number
// has)
for (intj = 1; j <= n; j++) {
nextTerm = nextTerm + terms.get(i - j);
 }
terms.add(nextTerm);
i++;
 }
// when the control comes out of the while loop, there will be two conditions:
// either nextTerm will be equal to x or greater than x
// if equal, the given number is Keith, else not
return (nextTerm == x);
 }

// driver code
publicstaticvoidmain(String[] args) {
Scannerin = newScanner(System.in);
intn = 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.");
 }
in.close();
 }
}