2026/03/14

[LeetCode ] 20 Valid Parentheses

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class Solution {
public:
  std::unordered_map<char, char> parMap = {
    {')', '('},
    {']', '['},
    {'}', '{'}
  };
  std::unordered_set<char> leftParSet = {'(', '[', '{'};

  bool processRight(std::stack<char> &stack, char c) {
    cout << "right : c = " << c << endl;
    if (stack.size() == 0)
      return false;
    if (stack.top() != parMap[c])
      return false;
    stack.pop();
    return true;
  }
  
  bool isValid(string s) {
    std::stack<char> stack;
    for (char c : s)
      if (leftParSet.count(c)) 
        stack.push(c);
      else if (!processRight(stack, c)) 
        return false;
      
    return stack.size() == 0;
  }
};