[Solved] Given a string s containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[‘ and ‘]’, determine if the input string is valid.

Question

Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

An input string is valid if:

1. Open brackets must be closed by the same type of brackets.
2. Open brackets must be closed in the correct order.
3. Every close bracket has a corresponding open bracket of the same type.

Example 1:

Input: s = "()"
Output: true

Example 2:

Input: s = "()[]{}"
Output: true

Example 3:

Input: s = "(]"
Output: false

Constraints:

• 1 <= s.length <= 104
• s consists of parentheses only '()[]{}'.

Python Solution

class Solution:
    def isValid(self, s: str) -> bool:
        stack=[]
        boo = True

        for ch in s:
            if ch in '([{':
                stack.append(ch)
            elif ch in ')]}':
                try:
                    popped_element = stack.pop()
                except:
                    boo=False
                    break
                if popped_element=='(' and ch==')':
                    pass
                elif popped_element=='{' and ch=='}':
                    pass
                elif popped_element=='[' and ch==']':
                    pass
                else:
                    boo=False
                    break
        if len(stack)==0:
            return (boo)
        else:
            return (False)