poj 1041 John's trip 欧拉回路

题目链接

求给出的图是否存在欧拉回路并输出路径， 从1这个点开始， 输出时按边的升序输出。

将每个点的边排序一下就可以。

 #include <iostream>
 #include <vector>
 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 #include <cmath>
 #include <map>
 #include <set>
 #include <string>
 #include <queue>
 using namespace std;
 #define pb(x) push_back(x)
 #define ll long long
 #define mk(x, y) make_pair(x, y)
 #define lson l, m, rt<<1
 #define mem(a) memset(a, 0, sizeof(a))
 #define rson m+1, r, rt<<1|1
 #define mem1(a) memset(a, -1, sizeof(a))
 #define mem2(a) memset(a, 0x3f, sizeof(a))
 #define rep(i, n, a) for(int i = a; i<n; i++)
 #define fi first
 #define se second
 typedef pair<int, int> pll;
 const double PI = acos(-1.0);
 const double eps = 1e-;
 const int mod = 1e9+;
 const int inf = ;
 const int dir[][] = { {-, }, {, }, {, -}, {, } };
 vector <pll> v[];
 int de[], cnt, ans[], vis[];
 void add(int a, int b, int c) {
     v[a].pb(mk(c, b));
     de[a]++;
 }
 void dfs(int u) {
     int len = v[u].size();
     for(int i = ; i<len; i++) {
         int to = v[u][i].second;
         int e = v[u][i].fi;
         if(vis[e])
             continue;
         vis[e] = ;
         dfs(to);
         ans[cnt++] = e;
     }
 }
 int main()
 {
     int a, b, c;
     while() {
         scanf("%d%d", &a, &b);
         if(a+b==)
             break;
         scanf("%d", &c);
         for(int i = ; i<; i++)
             v[i].clear();
         mem(de);
         mem(vis);
         cnt = ;
         add(a, b, c);
         add(b, a, c);
         while() {
             scanf("%d%d", &a, &b);
             if(a+b==)
                 break;
             scanf("%d", &c);
             add(a, b, c);
             add(b, a, c);
         }
         int flag = ;
         for(int i = ; i<=; i++) {
             if(de[i]%==) {
                 flag = ;
                 break;
             }
             sort(v[i].begin(), v[i].end());
         }
         if(flag) {
             puts("Round trip does not exist.");
             continue;
         }
         dfs();
         for(int i = cnt-; i>; i--)
             cout<<ans[i]<<" ";
         cout<<ans[]<<endl;
     }
     return ;
 }