DFS——单词接龙

单词接龙

        首先预处理，用g数组来存储任意两个单词之间最长的重合部分，used数组来记录每个单词使用的次数，然后就是即可暴搜。

        

#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for(int i = a;i<n;i++)
#define per(i,a,n) for(int i = n-1;i>=a;i--)
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
#define yes cout<<"YES"<<'\n';
#define no cout<<"NO"<<'\n';
#define endl '\n';
#define R register
typedef vector<int> VI;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> PII;
typedef double db;
mt19937 mrand(random_device{}());
const ll MOD=1000000007;
int rnd(int x) {return mrand() % x;}
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;};
ll lcm(int a,int b){return a*b/gcd(a,b);};

int n;
string s[25];
int g[25][25];
int used[25];
int ans;

void dfs(string t,int last){
	ans=max(SZ(t),ans);
	used[last]++;
	rep(i,0,n){
		if(g[last][i]&&used[i]<2) dfs(t+s[i].substr(g[last][i]),i);
	}
	used[last]--;
}

int main(){
	ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin>>n;
	rep(i,0,n) cin>>s[i];
	char st;
	cin>>st;
	rep(i,0,n){
		rep(j,0,n){
			auto a=s[i],b=s[j];
			rep(k,1,min(SZ(a),SZ(b))){
				if(a.substr(SZ(a)-k)==b.substr(0,k)){
					g[i][j]=k;
					break;
				}
			}
		}
	}
	rep(i,0,n){
		if(s[i][0]==st) dfs(s[i],i);
	}
	cout<<ans<<endl;
	return 0;
}