Merge pull request neetcode-gh#2193 from su5kk/patch-1

Update 0020-valid-parentheses.cpp
nick322 · Feb 1, 2023 · 5bc1a36 · 5bc1a36
2 parents e196f53 + f70f5a7
commit 5bc1a36
Showing 1 changed file with 13 additions and 14 deletions.
diff --git a/cpp/0020-valid-parentheses.cpp b/cpp/0020-valid-parentheses.cpp
@@ -12,30 +12,29 @@ class Solution {
 public:
  bool isValid(string s) {
  stack<char> open;
+ unordered_map<char, char> parens = {
+ {')', '('},
+ {']', '['},
+ {'}', '{'},
+ };
 
- for (int i = 0; i < s.size(); i++) {
- if (s[i] == ')' || s[i] == '}' || s[i] == ']') {
+ for (const auto& c : s) {
+ if (parens.find(c) != parens.end()) {
+ // if input starts with a closing bracket.
  if (open.empty()) {
  return false;
  }
- if (s[i] == ')' && open.top() != '(') {
- return false;
- }
- if (s[i] == '}' && open.top() != '{') {
- return false;
- }
- if (s[i] == ']' && open.top() != '[') {
+
+ if (open.top() != parens[c]) {
  return false;
  }
+
  open.pop();
  } else {
- open.push(s[i]);
+ open.push(c);
  }
  }
 
- if (!open.empty()) {
- return false;
- }
- return true;
+ return open.empty();
  }
 };