Valid Parentheses

hasValidParenthesis.swift

class Solution {
    
    var remaining : [String: Int] = ["(": 0, "[": 0, "{": 0]
    func isValid(_ s: String) -> Bool {
        let validChars = ["(", ")", "[", "]","{", "}"]
        let opens = ["[", "(", "{"]
        let closes = ["]", ")", "}"]
        
        for c in s {
            let c = String(c)
            guard remainingCloseFor(c) >= 0 else {
                print("1")
                return false
            }
        }
        for (_, val) in remaining {
            guard val == 0 else { 
                print("2")
                return false
            }
        }
        return true
    }
    var lastOpenedStack: [String] = []
    func remainingCloseFor(_ char: String) -> Int {
        // opening
        if let val = remaining[char] {
            remaining[char] = val + 1
            lastOpenedStack.append(char)
            return remaining[char]!
        } else {
            // closing
            let correspondingOpen: String
            if char == ")" {                
                remaining["("] = remaining["("]! - 1
                correspondingOpen = "("
                if lastOpenedStack.last != "(" {
                    remaining["("] = -1
                    print("4")
                } else {
                    lastOpenedStack.removeLast()
                }
            } else if char == "]" {
                remaining["["] = remaining["["]! - 1
                correspondingOpen = "["
                if lastOpenedStack.last != "[" {
                    remaining["["] = -1
                    print("5")
                } else {
                    lastOpenedStack.removeLast()
                }
            } else {
                remaining["{"] = remaining["{"]! - 1
                correspondingOpen = "{"
                if lastOpenedStack.last != "{" {
                    remaining["{"] = -1
                    print("6", lastOpenedStack)
                }else {
                    lastOpenedStack.removeLast()
                }
            }
            return remaining[correspondingOpen]!
        }
    }
    
    // What I learned: 
    // When I close, it has to be for last opened items
    // When something requires 'last' foo, then it might be a good indication that a stack is needed. 
    // If we need to pop the last item and go to a previous item, then 110% a stack is needed
    // If you're trying to build relationships then dictionaries are the best. 
    // DON'T BE AFRAID TO CREATE MULTIPLE STATE HOLDING VARIABLES. 
    // DON'T TRY TO ENCAPSULATE ALL STATES INTO A SINGLLE MASSIVE VARIABLE
    // Anything that causes an exit, return `false` can perhap be bubbled up/out
    
}

That being said, I believe there should be solutions with less code