1249. Minimum Remove to Make Valid Parentheses

leetcode1249.swift

class Solution {
    func minRemoveToMakeValid(_ s: String) -> String {
        var array = s.map { String($0) }
        
        var leftBraces = [Int]()
        
        for i in 0..<array.count {
            if array[i] == "(" {
                leftBraces.append(i)
                continue
            }
            if array[i] == ")" {
                if leftBraces.isEmpty  {
                    array[i] = ""
                } else {
                    leftBraces.removeLast()
                }
            }
        }
        
        for i in leftBraces {
            array[i] = ""
        }
        
        return array.joined()
    }
}