Prefix goodness 定义为字符串集合中公共前缀长度乘上拥有该公共前缀的字符串数量.让你求Prefix goodness的最大值.

放字典树里随便搞搞就好了.

#include <bits/stdc++.h>
using namespace std;
struct Trie {
    Trie * next[3];
    int cnt[3];
    Trie() {
        memset(next, 0, sizeof(next));
        memset(cnt, 0, sizeof(cnt));
    }
} * head;
int ans;
void insert(char *s)
{
    int d = 0;
    Trie * p = head;
    while (*s) {
        int c = *s++ - '0';
        if (p->next[c] == NULL) {
            p->next[c] = new Trie();
        }
        p = p->next[c];
        p->cnt[c]++;
        d++;
        ans = max(ans, d * p->cnt[c]);
    }
}
int main()
{
    int t;
    scanf("%d", &t);
    while (t--) {
        int n;
        ans = 0;
        scanf("%d", &n);
        head = new Trie();
        for (int i = 0; i < n; i++) {
            char str[205];
            scanf("%s", str);
            insert(str);
        }
        printf("%d\n", ans);
    }
    return 0;
}