'commit'

TangDou/LanQiaoBei/LanQiaoSTEMA202008/DaKuoHao_3.cpp

@@ -0,0 +1,31 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+int n;
+int res;
+stack<char> stk;
+bool check(string t) {
+    stack<char>().swap(stk);
+    for (int i = t.size() - 1; i >= 0; i--) {
+        if (!stk.empty() && stk.top() == '}' && t[i] == '{')
+            stk.pop();
+        else
+            stk.push(t[i]);
+    }
+    return stk.size() == 0;
+}
+void dfs(int u, string t) {
+    if (u == 2 * n + 1) {
+        if (check(t)) res++;
+        return;
+    }
+
+    dfs(u + 1, t + "{");
+    dfs(u + 1, t + "}");
+}
+int main() {
+    cin >> n;
+    dfs(1, "");
+    cout << res << endl;
+    return 0;
+}