Leetcode 20. Valid Parentheses

https://leetcode.com/problems/valid-parentheses/

When concerning ordering, stack is a good data structure to use.

Solution:

# T:O(n) S:O(1)
class Solution:
    # @param {string} s
    # @return {boolean}
    def isValid(self, s):
        dict, stk, N = {')':'(',']':'[','}':'{'}, [], len(s)
        for ch in s:
            if ch in dict.values():
                stk.append(ch)
            else:
                if not stk or stk.pop() != dict[ch]:
                    return False
        return not stk

Run Time: 48 ms