Valid Parentheses

Description:

Given a string 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.

Note that an empty string is also considered valid.

Example 1:

Input: "()"
Output: true

Example 2:

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

Example 3:

Input: "(]"
Output: false

Example 4:

Input: "([)]"
Output: false

Example 5:

Input: "{[]}"
Output: true

 bool isValid(string s) 
    {
        stack<char> parentheses;  // 定義一個棧
        for (int i = 0; i < s.size(); ++i) 
        {
            if (s[i] == '(' || s[i] == '[' || s[i] == '{') parentheses.push(s[i]);  // 如果是左括號 入棧
            else 
            {
                if (parentheses.empty()) return false;      // 如果為空 返回false
                if (s[i] == ')' && parentheses.top() != '(') return false;  // 有括號與站定匹配 不匹配返回false
                if (s[i] == ']' && parentheses.top() != '[') return false;
                if (s[i] == '}' && parentheses.top() != '{') return false;
                parentheses.pop();
            }
        }
        return parentheses.empty(); // 若棧為空則為true
        
    }