How do you solve Find the Key of the Numbers on LeetCode?

Find the Key of the Numbers (LeetCode #3270) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(1) time complexity and O(1) space complexity. Key insight: Understanding how to manipulate numbers and strings is crucial for solving digit-related problems.

What is the brute force solution for Find the Key of the Numbers?

The brute force approach for Find the Key of the Numbers is Brute Force, with O(1) time complexity and O(1) space complexity. The brute force approach involves converting each number into a four-digit string, padding with leading zeros if necessary, and then comparing the corresponding digits to find the smallest one. This is straightforward but not the most efficient. The optimal Optimal Solution approach improves this to O(1).

What algorithm or data structure is used to solve Find the Key of the Numbers?

Find the Key of the Numbers uses the following concepts: Math. The recommended patterns to study are: Array, String Manipulation.

What are the interview tips for Find the Key of the Numbers?

Always clarify the input constraints and edge cases before jumping into coding. Think about both string and numeric manipulations; sometimes one is more efficient than the other. Practice explaining your thought process while coding, as communication is key in interviews.

What are common mistakes when solving Find the Key of the Numbers?

Failing to pad numbers correctly, leading to incorrect digit comparisons. Not converting the final key back to an integer, which can lead to leading zeros in the output.

#3270

Find the Key of the Numbers

Easy

MathArrayString Manipulation

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

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

💡

Intuition

Time O(1)Space O(1)

The optimal solution is similar to the brute force approach but focuses on minimizing operations. Instead of converting to strings and padding, we can directly extract digits using mathematical operations, which is more efficient.

⚙️

Algorithm

4 steps

1Step 1: For each number, extract each digit using modulus and division by 10.
2Step 2: Store the digits in an array for easy access.
3Step 3: Compare the corresponding digits of the three numbers to find the minimum for each position.
4Step 4: Construct the key and return it as an integer.

solution.py10 lines

1def findKey(num1, num2, num3):
2    digits = [[0]*4 for _ in range(3)]
3    for i, num in enumerate([num1, num2, num3]):
4        for j in range(4):
5            digits[i][3-j] = num % 10
6            num //= 10
7    key = ''
8    for j in range(4):
9        key += str(min(digits[0][j], digits[1][j], digits[2][j]))
10    return int(key)

ℹ

Complexity note: The time complexity remains O(1) as we are still processing a fixed number of digits. The space complexity is O(1) since we are using a fixed-size array to store digits.

1Understanding how to manipulate numbers and strings is crucial for solving digit-related problems.
2Recognizing that leading zeros can be handled through string formatting or mathematical operations can simplify the solution.

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