feat: 添加P8905.cpp和P3102.cpp两个题目解答

添加了两个编程题目的解答代码文件，分别处理图论问题和字符串匹配问题

src/11/13/P3102.cpp

@@ -0,0 +1,34 @@
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <istream>
+#include <string>
+using ll = int64_t;
+
+std::string s;
+ll ans;
+
+int main(){
+    std::cin.tie(nullptr);
+    std::iostream::sync_with_stdio(false);
+
+    std::cin>>s;
+    for(ll i=1;i<s.size();i++){
+        ll l1=i,l2=s.size()-i;
+        for(ll j=0;j<std::min(l1,l2);j++){
+            if(s[j]!=s[i+j]){
+                goto nxt1;
+            }
+        }
+        ans++;
+        nxt1:;
+        for(ll j=0;j<std::min(l1,l2);j++){
+            if(s[i-1-j]!=s[s.size()-1-j]){
+                goto nxt2;
+            }
+        }
+        ans++;
+        nxt2:;
+    }
+    std::cout<<ans*2<<"\n";
+}

src/11/13/P8905.cpp

@@ -0,0 +1,28 @@
+#include <cstdint>
+#include <iostream>
+#include <istream>
+#include <vector>
+using ll = int64_t;
+
+ll n,m;
+struct P{
+    ll u,v;
+};
+std::vector<std::vector<P>> a; 
+std::vector<ll> f;
+
+int main(){
+    std::iostream::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    std::cin>>n>>m;
+    a.resize(n+1);
+    f.resize(n+1);
+    for(ll i=1;i<=m;i++){
+        ll u,v;
+        std::cin>>u>>v;
+        f[u]++,f[v]++;
+        a[u].emplace_back(v);
+        a[v].emplace_back(u);
+    }
+}