text: Nontrivial undulant Numbers | Java implementation to check if N is a Nontrivial undulant number ; Function to check if a string is double string or not ; a and b should not be equal ; Condition to check if length is odd make length even ; First half of s ; Second half of s ; Double string if first and last half are equal ; Function to check if N is an Nontrivial undulant number ; Driver code
code: class GFG { static boolean isDouble ( int num ) { String s = Integer . toString ( num ) ; int l = s . length ( ) ; if ( s . charAt ( 0 ) == s . charAt ( 1 ) ) return false ; if ( l % 2 == 1 ) { s = s + s . charAt ( 1 ) ; l ++ ; } String s1 = s . substring ( 0 , l / 2 ) ; String s2 = s . substring ( l / 2 ) ; return s1 . equals ( s2 ) ; } static boolean isNontrivialUndulant ( int N ) { return N > 100 && isDouble ( N ) ; } public static void main ( String [ ] args ) { int n = 121 ; if ( isNontrivialUndulant ( n ) ) { System . out . println ( " Yes " ) ; } else { System . out . println ( " No " ) ; } } }