題目：[...] (https://www.luogu.org/problemnew/show/P1019)

[Code:]

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;

int n, len[21];
int ans, used[21];
string s[21];
char head;

inline int pipei(string a, string b) {
    int lena = a.size(), lenb = b.size();
    int
 
 ret = 0, l = min(lena, lenb);
    for(int i=0; i<l; ++i) {
        if(a.substr(lena-i-1, i+1) == b.substr(0, i+1)) return i+1;
    }
    return 0;
}

void dfs(int sum, string now) {
    ans = max(ans, sum);
    for(int i=1; i<=n; ++i) {
        if(used[i] < 2) {
            int k = pipei(now, s[i]);
            if
 
(k == 0 || k == len[i]) continue;
            ++used[i];
            int l = now.size();
            string tmp = now;
            for(int j=k; j<len[i]; ++j) {
                now += s[i][j];
            }
            dfs(sum + len[i] - k, now);
            --used[i];
            now = tmp;
        }
    }
}

int
 
 main() {
    cin >> n;
    for(int i=1; i<=n; ++i) {
        cin >> s[i];
        len[i] = s[i].size();
    }
    cin >> head;
    for(int i=1; i<=n; ++i) {
        if(s[i][0] == head) {
            used[i] = 1; dfs(len[i], s[i]);
            used[i] = 0;
        }
    }
    printf("%d", ans);
    
    return 0;
}

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