Is Clear Digits easy or hard?

Clear Digits is classified as an Easy problem on LeetCode with a high acceptance rate. The challenge mainly tests whether you recognize the stack pattern used to remove the most recent character when processing a string.

Clear Digits Python/Java solution

Python and Java implementations typically use a list or stack-like structure. Iterate through the string, append letters, and pop the last element when a digit appears. This approach keeps the runtime O(n) and the implementation concise.

How to solve Clear Digits in O(n)?

Scan the string from left to right while maintaining a stack or simulated stack. Push letters onto the structure and remove the most recent letter whenever a digit appears. Because every character triggers at most one push or pop, the entire process runs in O(n) time.

What is the best approach for Clear Digits?

The stack-based simulation is the most common solution. Traverse the string, push letters onto a stack, and pop one letter whenever a digit appears. This directly models the rule that a digit removes the closest character to its left. The algorithm runs in O(n) time and O(n) space.

Is Clear Digits asked at Google/Amazon/Meta?

Clear Digits follows a classic stack simulation pattern frequently used in interviews at companies like Amazon, Google, and Meta. While the exact problem may vary, similar questions about removing previous elements or processing strings with stack logic appear often.

What data structure is used in Clear Digits?

A stack is the primary data structure used to solve Clear Digits efficiently. It allows constant-time removal of the most recent character, which matches the rule that each digit deletes the closest letter to its left.

What is the time complexity of Clear Digits?

The optimal time complexity is O(n), where n is the length of the string. Each character is processed exactly once. Stack push and pop operations are constant time, so the overall algorithm remains linear.

Description Hints 2 Solution Video 7:42

3174. Clear Digits

Easy82.7% acceptance5 companies

You are given a string s.

Your task is to remove all digits by doing this operation repeatedly:

Delete the first digit and the closest non-digit character to its left.

Return the resulting string after removing all digits.

Example 1:

Input: s = "abc"

Output: "abc"

Explanation:

There is no digit in the string.

Example 2:

Input: s = "cb34"

Output: ""

Explanation:

First, we apply the operation on s[2], and s becomes "c4".

Then we apply the operation on s[1], and s becomes "".

Constraints:

1 <= s.length <= 100
s consists only of lowercase English letters and digits.
The input is generated such that it is possible to delete all digits.

Asked at 5 companies

Flexera

Google Amazon Bloomberg Meta

Topics

Hints open one at a time

Hint 1

Process string s from left to right, if s[i] is a digit, mark the nearest unmarked non-digit index to its left.

Hint 2

Delete all digits and all marked characters.

7:42

Still stuck?Read 3 approaches, or watch a walkthrough.

Open solution

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1class Solution:
2    def clearDigits(self, s: str) -> str:
3        

Starter codePython 3Spaces: 4

Examples

Case 1Case 2

Input

"abc"

Input

"cb34"

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