Luogu 1341 无序字母对 - 欧拉路径

Solution

找一条字典序最小的欧拉路径。

用 $multiset$ 存储领接表。

欧拉路径模板传送门

Code

 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<set>
 using namespace std;

 const int N = 1e3 + ;

 int n, up = 'z' - 'A' + ;
 int ans[N], tot, d[N], num;

 multiset<int> to[N];

 void dfs(int u) {
     multiset<int> :: iterator i;
     for (i = to[u].begin(); i != to[u].end(); i = to[u].begin()) {
         int nt = *i;
         to[nt].erase(to[nt].find(u));
         to[u].erase(to[u].find(nt));
         dfs(nt);
     }
     ans[++tot] = u;
 }

 int main()
 {
     scanf("%d", &n);
     for (int i = ; i <= n; ++i) {
         char s[];
         scanf("%s", s);
         to[s[] - 'A' + ].insert(s[] - 'A' + );
         to[s[] - 'A' + ].insert(s[] - 'A' + );
         d[s[] - 'A' + ]++;
         d[s[] - 'A' + ]++;
     }
     for (int i = ; i <= up; ++i)
         if (d[i] & )
             num++;
     if (num ==  || num > )
         return puts("No Solution"), ;
     if (num == ) {
         for (int i = ; i <= up; ++i)
             if (d[i]) {dfs(i); break;}
     }
     else
         for (int i = ; i <= up; ++i)
             if (d[i] && (d[i] & )) {dfs(i); break;}
     for (int i = tot; i; i--)
         putchar(ans[i] + 'A' - );
     puts("");
 }