Largest Even Integer | Leetcode | Java solution (3798)

Today I solve the Largest Even String problem by iterating backwards through the string to find the last occurrence of the character '2'. Since the largest possible even number must end in an even digit (and retain the most significant digits), I return the substring up to that index, effectively removing only the trailing odd numbers.



3798. Largest Even Number

You are given a string s consisting only of the characters '1' and '2'.

You may delete any number of characters from s without changing the order of the remaining characters.

Return the largest possible resultant string that represents an even integer. If there is no such string, return the empty string "".



Example 1:

Input: s = "1112"

Output: "1112"

Explanation:

The string already represents the largest possible even number, so no deletions are needed.

Example 2:

Input: s = "221"

Output: "22"

Explanation:

Deleting '1' results in the largest possible even number which is equal to 22.

Example 3:

Input: s = "1"

Output: ""

Explanation:

There is no way to get an even number.



Constraints:

1 = s.length = 100
s consists only of the characters '1' and '2'.