洛谷 P1341 无序字母对(欧拉回路)

题目传送门

解题思路:

一道欧拉回路的模板题,详细定理见大佬博客,任意门

AC代码:

 #include<cstdio>
 #include<iostream>

 using namespace std;

 int ans[],du[],n,k = 0x7f7f7f,b[][],cnt = 0x3f,bj,tot;
 string l;

 inline void dfs(int x) {
     for(int i = ;i < ; i++)
         if(b[x][i]) {
             b[x][i] = b[i][x] = ;
             dfs(i);
         }
     ans[++tot] = x;
 }

 int main()
 {
     scanf("%d",&n);
     for(int i = ;i <= n; i++) {
         int x,y;
         cin >> l;
         x = l[] - 'A';
         y = l[] - 'A';
         k = min(k,min(x,y));
         b[x][y] = b[y][x] = ;
         du[x]++;
         du[y]++;
     }
     for(int i = ;i < ; i++)
         if(du[i] %  == ) {
             bj++;
             cnt = min(cnt,i);
         }
     if(bj == ) dfs(k);
     else if(bj == ) dfs(cnt);
     else {
         printf("No Solution");
         return ;
     }
     for(int i = tot;i >= ; i--)
         printf("%c",ans[i] + 'A');
     return ;
 }