LeetCode

3908. Valid Digit Number

We cast the number to a string to check for the digit while guarding against a leading match. The "cast-to-string for digit-level checks" trick is a Python staple worth pocketing.

1 chapter Beginner Written walk-through Updated 5 May 2026 Phil · @FirnoxGames

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1 3908. Valid Digit Number 📖 6 min read

We cast the number to a string to check for the digit while guarding against a leading match. The "cast-to-string for digit-level checks" trick is a Python staple worth pocketing.

In this chapter

Problem
String cast
No string cast

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Problem

You are given an integer n and a digit x.

A number is considered valid if:

It contains at least one occurrence of digit x, and
It does not start with digit x.

Return true if n is valid, otherwise return false.

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