refactor(P11670.cpp): 优化计算逻辑并重命名变量以提高可读性

- 将变量anumcnt重命名为apos和bpos以更清晰表达用途
- 重构计算逻辑，使用双指针方法替代原有循环
- 添加排序操作以提高计算效率

src/10/22/P11670.cpp

@@ -7,8 +7,8 @@
 using ll = int64_t;
 
 ll n,ans;
-std::vector<std::vector<ll>> anumcnt;
+std::vector<std::vector<ll>> apos,bpos;
-std::vector<ll> a;
+std::vector<ll> a,b;
 
 int main(){
     std::iostream::sync_with_stdio(false);
@@ -17,31 +17,37 @@ int main(){
     std::cin>>n;
 
     a.resize(n+1);
-    anumcnt.resize(n+1);
+    b.resize(n+1);
+    apos.resize(n+1);
+    bpos.resize(n+1);
 
     for(ll i=1;i<=n;i++){
         std::cin>>a[i];
-        anumcnt[a[i]].push_back(i);
+        apos[a[i]].push_back(std::min(i,n-i+1));
     }
     for(ll i=1;i<=n;i++){
-        ll b,nans=0;
+        std::cin>>b[i];
-        std::cin>>b;
+        bpos[b[i]].push_back(std::min(i,n-i+1));
-        if(a[i]==b){
-            ll N=i-1;
-            nans+=N*(N+1)/2;
-            N=n-i;
-            nans+=N*(N+1)/2;
-            // printf("a[%lld]==b[%lld], +=%lld\n",i,i,nans);
-        }
-        ans+=nans;
-        nans=0;
-        for(ll ai:anumcnt[b]){
-            ll l=std::min(ai,i);
-            ll r=std::min(n-ai+1,n-i+1);
-            nans += std::min(l,r);
-        }
-        // printf("b[%lld] l to r +=%lld\n",i,nans);
-        ans+=nans;
     }
+    for(ll i=1;i<=n;i++){
+        if(a[i]==b[i]){
+            ll N=i-1;
+            ans+=N*(N+1)/2;
+            N=n-i;
+            ans+=N*(N+1)/2;
+        }
+        std::sort(apos[i].begin(),apos[i].end());
+        std::sort(bpos[i].begin(),bpos[i].end());
+
+        ll pa=0,pb=0;
+        while(pa<apos[i].size() && pb<bpos[i].size()){
+            if(apos[i][pa]<bpos[i][pb]){
+                ans+=apos[i][pa++]*(bpos[i].size()-pb);
+            }else{
+                ans+=bpos[i][pb++]*(apos[i].size()-pa);
+            }
+        }
+    }
+
     std::cout<<ans<<"\n";
 }