leetcode-solution/20.valid-parentheses.cpp at master · oddway/leetcode-solution · GitHub

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/*
 * @lc app=leetcode id=20 lang=cpp
 *
 * [20] Valid Parentheses
 */

// @lc code=start

class Solution {
   public:
    bool isValid(string s) {
        // a stack for parentheses
        vector<char> parentheseStack;

        for (char c : s) {
            if (c == '(' || c == '{' || c == '[') {
                parentheseStack.push_back(c);
            }

            switch (c) {
                case ')':
                    if (parentheseStack.empty() ||
                        parentheseStack.back() != '(') {
                        return false;
                    }

                    parentheseStack.pop_back();
                    break;

                case '}':
                    if (parentheseStack.empty() ||
                        parentheseStack.back() != '{') {
                        return false;
                    }
                    parentheseStack.pop_back();
                    break;

                case ']':
                    if (parentheseStack.empty() ||
                        parentheseStack.back() != '[') {
                        return false;
                    }
                    parentheseStack.pop_back();
                    break;
                default:
                    break;
            }
        }

        return parentheseStack.empty();
    }
};
// @lc code=end