Is Valid Digit Number easy or hard?

Valid Digit Number is typically classified as an easy problem. The main challenge is recognizing that a single linear scan with simple character checks is sufficient, resulting in an O(n) solution with constant memory.

Valid Digit Number Python/Java solution

In Python, iterate through the string and use c.isdigit() or compare against '0' and '9'. In Java, use Character.isDigit(c) inside a loop or perform ASCII comparisons. Both implementations run in O(n) time and constant space.

How to solve Valid Digit Number in O(n)?

Iterate through the string and validate each character using a range check such as '0' <= c <= '9'. If any character fails the check, return false immediately. If the loop finishes without violations, the string represents a valid digit number.

What is the best approach for Valid Digit Number?

The most reliable approach is scanning the string once and checking that every character lies between '0' and '9'. This single-pass validation runs in O(n) time and O(1) space. It avoids regex overhead and clearly demonstrates how digit validation works at the character level.

Is Valid Digit Number asked at Google/Amazon/Meta?

Digit validation and string parsing problems frequently appear in screening rounds because they test attention to detail and basic algorithm design. Variations of numeric validation appear in interviews at companies like Amazon and Google, often as part of larger parsing problems.

What data structure is used in Valid Digit Number?

The solution mainly relies on basic string traversal rather than complex data structures. The algorithm processes characters sequentially and performs constant-time comparisons, making it a straightforward string validation task.

What is the time complexity of Valid Digit Number?

All common solutions run in O(n) time where n is the length of the string. Each character must be inspected at least once to confirm it is a digit. Space complexity is O(1) because the algorithm only uses a few variables during iteration.

3908. Valid Digit Number - Practice Online

Q: What is the best approach for Valid Digit Number?

The most reliable approach is scanning the string once and checking that every character lies between '0' and '9'. This single-pass validation runs in O(n) time and O(1) space. It avoids regex overhead and clearly demonstrates how digit validation works at the character level.

Q: Is Valid Digit Number asked at Google/Amazon/Meta?

Digit validation and string parsing problems frequently appear in screening rounds because they test attention to detail and basic algorithm design. Variations of numeric validation appear in interviews at companies like Amazon and Google, often as part of larger parsing problems.

Q: What data structure is used in Valid Digit Number?

The solution mainly relies on basic string traversal rather than complex data structures. The algorithm processes characters sequentially and performs constant-time comparisons, making it a straightforward string validation task.

Q: What is the time complexity of Valid Digit Number?

All common solutions run in O(n) time where n is the length of the string. Each character must be inspected at least once to confirm it is a digit. Space complexity is O(1) because the algorithm only uses a few variables during iteration.

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.

Example 1:

Input: n = 101, x = 0

Output: true

Explanation:

The number contains digit 0 at index 1. It does not start with 0, so it satisfies both conditions. Thus, the answer is true.

Example 2:

Input: n = 232, x = 2

Output: false

Explanation:

The number starts with 2, which violates the condition. Thus, the answer is false.

Example 3:

Input: n = 5, x = 1

Output: false

Explanation:

The number does not contain digit 1. Thus, the answer is false.

Constraints:

0 <= n <= 10⁵
0 <= x <= 9