Minimize String Length

Description

Given a string s, you have two types of operation:

- Choose an index i in the string, and let c be the character in position i. Delete the closest occurrence of c to the left of i (if exists).

- Choose an index i in the string, and let c be the character in position i. Delete the closest occurrence of c to the right of i (if exists).

Your task is to minimize the length of s by performing the above operations zero or more times.

Return an integer denoting the length of the minimized string.