Keith Number | C ++ program to check if a number is Keith or not ; Returns true if x is Keith , else false . ; Store all digits of x in a vector " terms " Also find number of digits and store in " n " . ; int temp = x , n = 0 ; n is number of digits in x ; To get digits in right order ( from MSB to LSB ) ; Keep finding next trms of a sequence generated using digits of x until we either reach x or a number greate than x ; Next term is sum of previous n terms ; When the control comes out of the while loop , either the next_term is equal to the number or greater than it . If next_term is equal to x , then x is a Keith number , else not ; Driver program
#include <bits/stdc++.h> NEW_LINE using namespace std ; bool isKeith ( int x ) { vector < int > terms ; while ( temp > 0 ) { terms . push_back ( temp % 10 ) ; temp = temp / 10 ; n ++ ; } reverse ( terms . begin ( ) , terms . end ( ) ) ; int next_term = 0 , i = n ; while ( next_term < x ) { next_term = 0 ; for ( int j = 1 ; j <= n ; j ++ ) next_term += terms [ i - j ] ; terms . push_back ( next_term ) ; i ++ ; } return ( next_term == x ) ; } int main ( ) { isKeith ( 14 ) ? cout << " Yes STRNEWLINE " : cout << " No STRNEWLINE " ; isKeith ( 12 ) ? cout << " Yes STRNEWLINE " : cout << " No STRNEWLINE " ; isKeith ( 197 ) ? cout << " Yes STRNEWLINE " : cout << " No STRNEWLINE " ; return 0 ; }