How should I practice Double-Base Palindromes?

Start by reading the full statement, solve the visible examples, then compare the pattern against related xAI phone screen problems in FastPrep.

Is Double-Base Palindromes associated with xAI?

FastPrep tags this as a xAI phone screen coding practice problem when the problem catalog has that company and stage context.

Problem · Math

Double-Base Palindromes

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● Easy

xAIFULLTIMEPHONE SCREEN

Problem statement

Given an integer upperBound, return every integer x such that 1 <= x <= upperBound and the ordinary representations of x in both base 10 and base 2 read the same forward and backward.

Binary representations must not contain leading zeroes. Return the qualifying integers in increasing order.

Function

doubleBasePalindromes(upperBound: int) → int[]

Examples

Example 1

upperBound = 20return = [1,3,5,7,9]

For example, 9 is 9 in decimal and 1001 in binary, so it qualifies. No integer from 10 through 20 is palindromic in both bases.

Example 2

upperBound = 100return = [1,3,5,7,9,33,99]

33 is 100001 in binary, and 99 is 1100011; both representations are palindromes.

Constraints

1 <= upperBound <= 100000.
Use each number's canonical decimal and binary representations without leading zeroes.