[LeetCode]#20. Valid Parentheses

Environment: Python 3.7

Key technique: .pop, dictionary

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.

Example 1:

Example 2:

Example 3:

Example 4:

Example 5:

Analysis:

  1. Create a mapping dictionary
  2. input your test example

3–4. get first element in s for stack dictionary

5–6. get second in s and top_element is stack element.

7–8 check mapping dictionary is same as top_element

9 return your result

Solution:

Submissions:

Reference:

Note:

Very hard to me and I need check reference….

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