How do you solve Largest Odd Number in String on LeetCode?

Largest Odd Number in String (LeetCode #1903) 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: The largest odd number can be determined by the last odd digit in the string.

What is the time complexity of Largest Odd Number in String?

The optimal solution for Largest Odd Number in String runs in O(n) time and uses O(1) space. This complexity is linear because we only traverse the string once, looking for the last odd digit.

What is the brute force solution for Largest Odd Number in String?

The brute force approach for Largest Odd Number in String is Brute Force, with O(n²) time complexity and O(1) space complexity. The brute-force approach involves generating all possible non-empty substrings of the given string and checking each one to see if it's an odd number. This is straightforward but inefficient for larger strings. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Largest Odd Number in String?

Largest Odd Number in String uses the following concepts: Math, String, Greedy. The recommended patterns to study are: Greedy, String Manipulation.

What are the interview tips for Largest Odd Number in String?

Always think about the simplest approach first before optimizing. Consider edge cases like strings with no odd digits. Practice identifying patterns in problems to improve your problem-solving speed.

What are common mistakes when solving Largest Odd Number in String?

Not considering that the largest odd number is determined by the last odd digit. Overcomplicating the problem by generating all substrings instead of focusing on the last odd digit.

#1903

Largest Odd Number in String

Easy

MathStringGreedyGreedyString Manipulation

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(1)

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Intuition

Time O(n)Space O(1)

Instead of generating all substrings, we can directly look for the last odd digit in the string. The largest odd number will always be the substring from the start of the string to this last odd digit.

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Algorithm

3 steps

1Step 1: Initialize a variable to store the result as an empty string.
2Step 2: Iterate through the string from the end to the beginning.
3Step 3: If an odd digit is found, set the result to the substring from the start to this digit and break the loop.

solution.py7 lines

1num = '35427'
2result = ''
3for i in range(len(num) - 1, -1, -1):
4    if int(num[i]) % 2 == 1:
5        result = num[:i + 1]
6        break
7print(result)

ℹ

Complexity note: This complexity is linear because we only traverse the string once, looking for the last odd digit.

1The largest odd number can be determined by the last odd digit in the string.
2We can avoid unnecessary checks by iterating from the end of the string.

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