#1963
Minimum Number of Swaps to Make the String Balanced
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two pointers · string · stack · greedy
Description
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.
Example 1:
Input: s = "][]["
Output: 1
Explanation: You can make the string balanced by swapping index 0 with index 3.
The resulting string is "[[]]".
Example 2:
Input: s = "]]][[["
Output: 2
Explanation: You can do the following to make the string balanced:
- Swap index 0 with index 4. s = "[]][][".
- Swap index 1 with index 5. s = "[[][]]".
The resulting string is "[[][]]".
Example 3:
Input: s = "[]"
Output: 0
Explanation: The string is already balanced.
Solution