Check If Digits Are Equal in String After Operations I Python/Java solution

The solution converts the string to a list of integers and simulates the reduction process. For each round, compute (digits[i] + digits[i+1]) % 10 and overwrite or build the next list until only two digits remain. The same logic works in Python, Java, C++, Go, and TypeScript with O(n^2) time complexity.

How to solve Check If Digits Are Equal in String After Operations I in O(n)?

Most implementations use O(n^2) simulation because the string shrinks gradually. A theoretical O(n) method can be derived by expressing the final digits as weighted sums using binomial coefficients modulo 10, but that level of optimization is usually unnecessary for this version of the problem.

What is the best approach for Check If Digits Are Equal in String After Operations I?

The most practical approach is simulation. Convert the string into digits and repeatedly replace each adjacent pair with (a + b) % 10 until only two digits remain. An in‑place simulation keeps the time complexity at O(n^2) while reducing space usage to O(1).

Is Check If Digits Are Equal in String After Operations I asked at Google/Amazon/Meta?

Problems involving digit transformations and iterative reductions appear in interviews at companies like Google, Amazon, and Meta. Variants test your ability to simulate processes on arrays or strings and sometimes recognize the combinatorial pattern behind repeated pair operations.

What data structure is used in Check If Digits Are Equal in String After Operations I?

The core structure is a simple array or list of digits derived from the input string. The algorithm repeatedly iterates over this array, updating each position with the sum of adjacent digits modulo 10.

What is the time complexity of Check If Digits Are Equal in String After Operations I?

The standard simulation runs in O(n^2) time. Each operation shortens the string by one, and every step processes the remaining digits, producing roughly n + (n−1) + ... + 2 computations. Space complexity ranges from O(n) with a temporary array to O(1) with an in‑place implementation.

Description Hints 1 Solution Video 42:11

3461. Check If Digits Are Equal in String After Operations I

Q: Is Check If Digits Are Equal in String After Operations I easy or hard?

The problem is classified as Easy. The main challenge is recognizing that the operation simply reduces the array step by step, which can be implemented directly with a simulation loop.

Easy82.5% acceptance4 companies

You are given a string s consisting of digits. Perform the following operation repeatedly until the string has exactly two digits:

For each pair of consecutive digits in s, starting from the first digit, calculate a new digit as the sum of the two digits modulo 10.
Replace s with the sequence of newly calculated digits, maintaining the order in which they are computed.

Return true if the final two digits in s are the same; otherwise, return false.

Example 1:

Input: s = "3902"

Output: true

Explanation:

Initially, s = "3902"
First operation:
- (s[0] + s[1]) % 10 = (3 + 9) % 10 = 2
- (s[1] + s[2]) % 10 = (9 + 0) % 10 = 9
- (s[2] + s[3]) % 10 = (0 + 2) % 10 = 2
- s becomes "292"
Second operation:
- (s[0] + s[1]) % 10 = (2 + 9) % 10 = 1
- (s[1] + s[2]) % 10 = (9 + 2) % 10 = 1
- s becomes "11"
Since the digits in "11" are the same, the output is true.

Example 2:

Input: s = "34789"

Output: false

Explanation:

Initially, s = "34789".
After the first operation, s = "7157".
After the second operation, s = "862".
After the third operation, s = "48".
Since '4' != '8', the output is false.

Constraints:

3 <= s.length <= 100
s consists of only digits.

Asked at 4 companies

Amazon

Google Microsoft Meta

Topics

Hints open one at a time

Hint 1

Simulate the operations as described.

42:11

Still stuck?Read the written solution, or watch a walkthrough.

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

Starter codePython 3Spaces: 4

Examples

Case 1Case 2

Input

"3902"

Input

"34789"

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