ValidParentheses.kt

import java.util.Stack

/**
 * Given a string containing just the characters '(', ')', '{', '}', '[' and ']',
 * determine if the input string is valid.
 * The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]" are not.
 *
 * Accepted.
 */
class ValidParentheses {

    fun isValid(s: String): Boolean {
        if (s.isEmpty() || s.length == 1) {
            return false
        }

        val stack = Stack<Char>()
        for (c in s.toCharArray()) {
            if (!stack.isEmpty() && (c == ')' && stack.peek() == '('
                            || c == ']' && stack.peek() == '['
                            || c == '}' && stack.peek() == '{')) {
                stack.pop()
            } else {
                stack.push(c)
            }
        }

        // println(stack)

        return stack.isEmpty()
    }

}