1544. Make The String Great - Explanation

class Solution:
    def makeGood(self, s: str) -> str:
        n = len(s)
        i = 0
        while i < n:
            if i and s[i] != s[i - 1] and s[i].lower() == s[i - 1].lower():
                s = s[:i - 1] + s[i + 1:]
                n -= 2
                i -= 2
            i += 1
        return s

class Solution:
    def makeGood(self, s: str) -> str:
        def lower(c):
            if ord(c) < ord('a'):
                return chr(ord('a') + ord(c) - ord('A'))
            return c

        stack = []
        i = 0
        while i < len(s):
            if stack and stack[-1] != s[i] and lower(stack[-1]) == lower(s[i]):
                stack.pop()
            else:
                stack.append(s[i])
            i += 1
        return "".join(stack)

class Solution:
    def makeGood(self, s: str) -> str:
        stack = []
        for i in range(len(s)):
            if stack and abs(ord(s[i]) - ord(stack[-1])) == 32:
                stack.pop()
            else:
                stack.append(s[i])
        return "".join(stack)

class Solution:
    def makeGood(self, s: str) -> str:
        l = 0
        s = list(s)
        for r in range(len(s)):
            if l > 0 and abs(ord(s[r]) - ord(s[l - 1])) == 32:
                l -= 1
            else:
                s[l] = s[r]
                l += 1
        return ''.join(s[:l])