괄호[BOJ]

for _ in 0..<Int(readLine()!)! {
    var list: [Character] = []
    var check = true

    let input = readLine()!
    for char in input {
        if char == "(" {
            list.append(char)
        } else {
            if list.isEmpty {
                check = false
                break
            } else {
                list.removeLast()
            }
        }
    }
    if check == false {
        print("NO")
    } else {
        print(list.isEmpty ? "YES" : "NO")
    }
}

시간복잡도: O(n²)