一开始蠢了，想着直接看最后一个，其实直接边插边搞就好了～

#include<iostream>
#include<vector>
#include<cstring>
#include<map>
using namespace std;
using ll = long long;const int M = 2e6+10;
struct Trie{int x[10],num;
}tree[M];
int cnt = 1;
int res;map<char,int>mp;void pre()
{for(int i=0;i<=cnt;i++){for(int j=0;j<=8;++j)tree[i].x[j] = 0;tree[i].num  = 0;}cnt = 1;
}
int getnum(char c){return mp[c];
}void insert(string t)
{int pos = 1;int len = t.size();for(int i=0;i<len;++i){int num = getnum(t[i]);if(!tree[pos].x[num])tree[pos].x[num] = ++cnt;pos = tree[pos].x[num];tree[pos].num++;res = max(tree[pos].num*(i+1),res);}}int main()
{mp['A'] = 1;mp['C'] = 2;mp['G'] = 3;mp['T'] = 4;int _;cin>>_;int ct = 0;while(_--){pre();ct++;res = 0;int t;cin>>t;for(int i=1;i<=t;++i){string s;cin>>s;insert(s);if(i==t)printf("Case %d: %d\n",ct,res);}}}