s0020

src/s0020_valid_parentheses.cpp

@@ -0,0 +1,26 @@
+#include "s0020_valid_parentheses.hpp"
+
+bool match(string s1, string s2) {
+  return s1 == "(" && s2 == ")" ||
+         s1 == "[" && s2 == "]" ||
+         s1 == "{" && s2 == "}";
+}
+
+// 直接用栈
+
+bool Solution::isValid(string s) {
+  stack<string> stack;
+  int len = s.length();
+  for (int i{0}; i < len; i++) {
+    if (stack.empty()) {
+      stack.push(s.substr(i, 1));
+    } else {
+      if (match(stack.top(), s.substr(i, 1))) {
+        stack.pop();
+      } else {
+        stack.push(s.substr(i, 1));
+      }
+    }
+  }
+  return stack.empty();
+}