Valid Parentheses

// Runtime 0ms (Beats 100%)
// Memory 6.3 MB (Beats 94.2%)
class Solution {
public:
    bool isValid(string s) {
        stack<char> seen;

        for (const auto ch : s) {
            if (ch == '(' || ch == '{' || ch == '[') {
                seen.emplace(ch);
                continue;
            }
            if (ch == ')') {
                if (seen.size() <= 0 || seen.top() != '(') {
                    return false;
                }
                seen.pop();
            }
            else if (ch == '}') {
                if (seen.size() <= 0 || seen.top() != '{') {
                    return false;
                }
                seen.pop();
            }
            else if (ch == ']') {
                if (seen.size() <= 0 || seen.top() != '[') {
                    return false;
                }
                seen.pop();
            } else {
                continue;
            }
        }
        return seen.size() == 0;
    }
};

# Runtime: 34ms (Beats 83%)
# Memory: 16.37 MB (Beats 30%)
class Solution:
    def isValid(self, s: str) -> bool:
        stack = []
        for c in s:
            if c in ['(', '{', '[']:
                stack.append(c)
                continue
            elif c == ')':
                if not len(stack):
                    return False
                top = stack[-1]
                if top != '(':
                    return False
            elif c == '}':
                if not len(stack):
                    return False
                top = stack[-1]
                if top != '{':
                    return False
            elif c == ']':
                if not len(stack):
                    return False
                top = stack[-1]
                if top != '[':
                    return False
            else:
                continue
            stack.pop()
        return len(stack) == 0