Link to Question

EASY

Valid Parentheses

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

Input:

s = "()[]{}"

Output:

true

Explanation:
All brackets are closed in the correct order.

---

Constraints

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

---

Solution: Stack

• Time Complexity: O(n)
• Space Complexity: O(n)

C++

class Solution {
public:
    bool isValid(string s) {
        string temp;
        unordered_map<char, char> m = {{')', '('}, {']', '['}, {'}', '{'},};
        for (auto c : s) {
            if (!m.count(c)) temp+= c;
            else {
                if (temp.empty() || temp.back() != m[c]) return false;
                temp.pop_back();
            }
        }
        return temp.size() == 0;
    }
};