Trie Algorithm (LOJ 1224 DNA Prefix)

/******Trie ALGO Problem (LOJ 1224)******
Given N string (Contain only 'A', 'C', 'G', 'T').
Find a prefix which is Maximum len*time.
    (Here len=Prefix size, time=Occur time).
°°°Input°°
1 4
ACGT ACGTGCGT ACCGTGC ACGCCGT
°°°Output°°°
Case 1: 9
*/
#include <iostream>
using namespace std;
int ans;
struct trie{
    trie *eg[5]; int c=0;
    trie(){eg[1]=eg[2]=eg[3]=eg[4]=NULL;}
};
int idx(char c){
    if (c=='A') return 1; if (c=='C') return 2;
    if (c=='G') return 3; if (c=='T') return 4;
}
void insert(char s[],trie *r){
    trie *t=r; int l=strlen(s);
    for (int i=0; i<l; i++){
        int x=idx(s[i]);
        if (!t->eg[x]) t->eg[x]=new trie();
        t=t->eg[x], t->c++;
    }
}
void dfs(int p,trie *r){
    ans=max(ans,p*r->c);
    for (int i=1; i<5; i++)
        if (r->eg[i]) dfs(p+1, r->eg[i]);
}
void clean(trie *t){
    for (int i=1; i<5; i++)
        if (t->eg[i]) clean(t->eg[i]);
    free(t);
}
int main(){
    int t,cs=1,n;
    char s[60];
    scanf("%d",&t);
    while (t--){
        trie *r=new trie();
        scanf("%d",&n);
        while (n--) scanf("%s",s), insert(s,r);
        ans=0, dfs(0,r);
        printf("Case %d: %d\n",cs++,ans);
        clean(r);
    } return 0;
}