How do you solve Concatenate Non-Zero Digits and Multiply by Sum I on LeetCode?

Concatenate Non-Zero Digits and Multiply by Sum I (LeetCode #3754) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(1) space complexity. Key insight: Non-zero digits are crucial for forming x.

What is the time complexity of Concatenate Non-Zero Digits and Multiply by Sum I?

The optimal solution for Concatenate Non-Zero Digits and Multiply by Sum I runs in O(n) time and uses O(1) space. This is O(n) because we process each digit once, but we use constant space for variables.

What is the brute force solution for Concatenate Non-Zero Digits and Multiply by Sum I?

The brute force approach for Concatenate Non-Zero Digits and Multiply by Sum I is Brute Force, with O(n) time complexity and O(n) space complexity. Extract each digit, check if it's non-zero, and build the new integer. Then calculate the sum of its digits and multiply. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Concatenate Non-Zero Digits and Multiply by Sum I?

Concatenate Non-Zero Digits and Multiply by Sum I uses the following concepts: Math. The recommended patterns to study are: String Manipulation, Digit Manipulation.

What are the interview tips for Concatenate Non-Zero Digits and Multiply by Sum I?

Clarify the problem statement and constraints. Discuss edge cases upfront. Explain your thought process clearly while coding.

What are common mistakes when solving Concatenate Non-Zero Digits and Multiply by Sum I?

Forgetting to handle the case when there are no non-zero digits. Incorrectly calculating the sum of digits.

#3754

Concatenate Non-Zero Digits and Multiply by Sum I

Easy

MathString ManipulationDigit Manipulation

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n)	O(n)
Space	O(n)	O(1)

💡

Intuition

Time O(n)Space O(1)

Directly process the digits of n while calculating x and sum in one pass to improve efficiency.

⚙️

Algorithm

3 steps

1Step 1: Initialize x as 0 and sum as 0.
2Step 2: For each digit in n, if it's non-zero, update x and add to sum.
3Step 3: Return x * sum.

solution.py11 lines

1def concatenate_and_multiply(n):
2    x, sum_digits = 0, 0
3    factor = 1
4    while n > 0:
5        digit = n % 10
6        if digit != 0:
7            x = digit * factor + x
8            sum_digits += digit
9            factor *= 10
10        n //= 10
11    return x * sum_digits

ℹ

Complexity note: This is O(n) because we process each digit once, but we use constant space for variables.

1Non-zero digits are crucial for forming x.
2The sum of digits directly influences the final result.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.