'commit'

TangDou/LanQiaoBei/LanQiaoSTEMA202008/DaKuoHao_1.cpp

@@ -0,0 +1,24 @@
+#include <bits/stdc++.h>
+using namespace std;
+int n;
+int res;
+void dfs(int u, string t) {
+    if (u == 2 * n + 1) {
+        if (t.size() == 0) res++;
+        return;
+    }
+    //当前填充{
+    dfs(u + 1, t + "{");
+
+    if (t.back() == '{')             //如果t的最后一个字符是 {
+        t.pop_back(), dfs(u + 1, t); //当前填充},就会对掉一对{}
+    // t.substr(0,t.size()-1) 去掉尾巴
+    else
+        dfs(u + 1, t + "}");
+}
+int main() {
+    cin >> n;
+    dfs(1, "");
+    cout << res << endl;
+    return 0;
+}

TangDou/LanQiaoBei/LanQiaoSTEMA202008/DaKuoHao_2.cpp

@@ -0,0 +1,35 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+const int N = 1e5 + 10;
+
+int n;
+int res;
+
+char stk[N];
+bool check(string s) {
+    int tt = 0; // 因为是多次使用栈，所以这里tt需要每次清空为0
+    for (int i = s.size() - 1; i >= 0; i--) {
+        if (tt && stk[tt] == '}' && s[i] == '{')
+            tt--;
+        else
+            stk[++tt] = s[i];
+    }
+    return tt == 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;
+}

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;
+}