Leetcode 20 - Valid Parentheses

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

Valid Parentheses - LeetCode

 

Leetcode 20 - Valid Parentheses

 

문제 설명

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:

Input: s = "()" Output: true

Example 2:

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

Example 3:

Input: s = "(]" Output: false

Example 4:

Input: s = "([)]" Output: false

Example 5:

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

 

Constraints:

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

 

문제 풀이

class Solution {
public:
    bool isValid(string s) {
        stack<int> st;

        for (auto c : s)
        {
            if (c == '(' || c == '{' || c == '[')
            {
                st.push(c);
            }

            if (st.size() == 0)
                return false;

            if (c == ')')
            {
                if (st.top() == '(')
                    st.pop();
                else
                    return false;
            }

            if (c == '}')
            {
                if (st.top() == '{')
                    st.pop();
                else
                    return false;
            }

            if (c == ']')
            {
                if (st.top() == '[')
                    st.pop();
                else
                    return false;
            }
        }
        if (st.empty())
            return true;
        else
            return false;
    }
};