Minimum Number of Swaps to Make the String Balanced

You are given a 0-indexed string s of even length n. The string consists of exactly n / 2 opening brackets '[' and n / 2 closing brackets ']'.

A string is called balanced if and only if:

• It is the empty string, or

• It can be written as AB, where both A and B are balanced strings, or

• It can be written as [C], where C is a balanced string.

You may swap the brackets at any two indices any number of times.

Return the minimum number of swaps to make s balanced.

LeetCode Problem - 1963

class Solution {
    public int minSwaps(String s) {
        int openBracketCounter = 0; // Counter to track unmatched open brackets

        // Iterate through each character of the string
        for(char ch : s.toCharArray()){
            if(ch == '['){ // If the character is an open bracket
                openBracketCounter++; // Increment the open bracket counter
            } else if (openBracketCounter > 0){ // If we find a closing bracket and there are unmatched open brackets
                openBracketCounter--; // Match the closing bracket by decrementing the open bracket counter
            }
        }

        // Since each swap can fix two unmatched brackets, we divide by 2 (and add 1 to ensure rounding)
        return (openBracketCounter + 1) / 2; 
    }
}