Minimum Length of String After Deleting Similar Ends — LeetCode 1750 Python Solution

The problem

Given a string s consisting only of characters 'a', 'b', and 'c'. You are asked to apply the following algorithm on the string any number of times: Pick a non-empty prefix from the string s where all the characters in the prefix are equal.

Example

Input

s = "ca"

Output

2

Explanation

You can't remove any characters, so the string stays as is.

Python solution

class Solution:
    def minimumLength(self, s: str) -> int:
        i, j = 0, len(s) - 1
        while i < j and s[i] == s[j]:
            while i + 1 < j and s[i] == s[i + 1]:
                i += 1
            while i < j - 1 and s[j - 1] == s[j]:
                j -= 1
            i, j = i + 1, j - 1
        return max(0, j - i + 1)

Complexity

Pattern: Two Pointers

Use the order already in the input to discard half the search space at every step. LeetCode 1750. Minimum Length of String After Deleting Similar Ends is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Two Pointers.

The two pointers guide has the Python template for the pattern and the 201 LeetCode problems that use it.

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