Count Valid Digit Strings with Wildcards | Dataford Interview Questions

Given a string consisting of digits and '?' wildcards, count the number of valid string combinations where no two adjacent characters are identical. Examples: '001' outputs 0, '01?' outputs 2 (010, 012), '?1?' outputs 4 (010, 012, 110, 112), and '?1??' outputs 8.

Asked in the Round 5 (Global Manager) stage. This is a LeetCode Medium dynamic programming and string counting problem.

Implement count_valid_combinations(s). Each ? can be replaced by 0, 1, or 2. Return the exact number of replacements whose adjacent characters are all different. The input is a nonempty string containing only 0, 1, 2, and ?.

Constraints

1 <= len(s) <= 1000
Each character of s is one of 0, 1, 2, or ?
Each ? can be replaced only by 0, 1, or 2
Return the exact count without applying a modulus

Function Signature

def count_valid_combinations(s):

Your question is Count Valid Digit Strings with Wildcards. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

Asked in the Round 5 (Global Manager) stage. This is a LeetCode Medium dynamic programming and string counting problem.

Constraints

1 <= len(s) <= 1000
Each character of s is one of 0, 1, 2, or ?
Each ? can be replaced only by 0, 1, or 2
Return the exact count without applying a modulus

Function Signature

def count_valid_combinations(s):

Your question is Count Valid Digit Strings with Wildcards. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.