3561 - Resulting String After Adjacent Removals.

Medium

You are given a string s consisting of lowercase English letters.

You must repeatedly perform the following operation while the string s has at least two consecutive characters:

• Remove the leftmost pair of adjacent characters in the string that are consecutive in the alphabet, in either order (e.g., 'a' and 'b', or 'b' and 'a').

• Shift the remaining characters to the left to fill the gap.

Return the resulting string after no more operations can be performed.

Note: Consider the alphabet as circular, thus 'a' and 'z' are consecutive.

Example 1:

Input: s = "abc"

Output: "c"

Explanation:

• Remove "ab" from the string, leaving "c" as the remaining string.

• No further operations are possible. Thus, the resulting string after all possible removals is "c".

Example 2:

Input: s = "adcb"

Output: ""

Explanation:

• Remove "dc" from the string, leaving "ab" as the remaining string.

• Remove "ab" from the string, leaving "" as the remaining string.

• No further operations are possible. Thus, the resulting string after all possible removals is "".

Example 3:

Input: s = "zadb"

Output: "db"

Explanation:

• Remove "za" from the string, leaving "db" as the remaining string.

• No further operations are possible. Thus, the resulting string after all possible removals is "db".

Constraints:

• <code>1 <= s.length <= 10⁵</code>

• s consists only of lowercase English letters.