Euler Circuit UVA - 10735（混合图输出路径）

就是求混合图是否存在欧拉回路

如果存在则输出一组路径

（我就说嘛 咱的代码怎么可能错。。。。。最后的输出格式竟然w了一天 我都没发现）

解析：

　　对于无向边定向建边放到网络流图中add(u, v, 1);

　　对于有向边放到另一个图中add2(u, v);

　　然后就是混合边求是否有欧拉

　　一边dinic后 遍历每一条边 如果不是反向边 且 起点不是s 终点不是t

　　如果Node[i].c == 0 则 add2(Node[i].v, Node[i].u);

　　else add2(Node[i].u, Node[i].v);

　　然后用有向图的fleury输出边就好了

 #include <iostream>
 #include <cstdio>
 #include <sstream>
 #include <cstring>
 #include <map>
 #include <cctype>
 #include <set>
 #include <vector>
 #include <stack>
 #include <queue>
 #include <algorithm>
 #include <cmath>
 #include <bitset>
 #define rap(i, a, n) for(int i=a; i<=n; i++)
 #define rep(i, a, n) for(int i=a; i<n; i++)
 #define lap(i, a, n) for(int i=n; i>=a; i--)
 #define lep(i, a, n) for(int i=n; i>a; i--)
 #define rd(a) scanf("%d", &a)
 #define rlld(a) scanf("%lld", &a)
 #define rc(a) scanf("%c", &a)
 #define rs(a) scanf("%s", a)
 #define pd(a) printf("%d\n", a);
 #define plld(a) printf("%lld\n", a);
 #define pc(a) printf("%c\n", a);
 #define ps(a) printf("%s\n", a);
 #define MOD 2018
 #define LL long long
 #define ULL unsigned long long
 #define Pair pair<int, int>
 #define mem(a, b) memset(a, b, sizeof(a))
 #define _  ios_base::sync_with_stdio(0),cin.tie(0)
 //freopen("1.txt", "r", stdin);
 using namespace std;
 const int maxn = , INF = 2e9;
 int n, m, s, t, cnt;
 int in[maxn], out[maxn], vis[maxn];
 int d[maxn], head[maxn], cur[maxn];
 set<int> ss;
 int st[maxn],cnt3;
 int cnt2, head2[maxn];

 struct edge
 {
     int u, v, c, next, ff;
 }Edge[maxn << ];

 void add_(int u, int v, int c, int ff)
 {
     Edge[cnt].u = u;
     Edge[cnt].v = v;
     Edge[cnt].c = c;
     Edge[cnt].ff = ff;
     Edge[cnt].next = head[u];
     head[u] = cnt++;
 }

 void add(int u, int v, int c)
 {
     add_(u, v, c, );
     add_(v, u, , );
 }

 bool bfs()
 {
     queue<int> Q;
     mem(d, );
     Q.push(s);
     d[s] = ;
     while(!Q.empty())
     {
         int u = Q.front(); Q.pop();
         for(int i = head[u]; i != -; i = Edge[i].next)
         {
             edge e = Edge[i];
             if(!d[e.v] && e.c > )
             {
                 d[e.v] = d[e.u] + ;
                 Q.push(e.v);
                 if(e.v == t) return ;
             }
         }
     }
     return d[t] != ;
 }

 int dfs(int u, int cap)
 {
     int ret = ;
     if(u == t || cap == )
         return cap;
     for(int &i = cur[u]; i != -; i = Edge[i].next)
     {
         edge e = Edge[i];
         if(d[e.v] == d[u] +  && e.c > )
         {
             int V = dfs(e.v, min(cap, e.c));
             Edge[i].c -= V;
             Edge[i^].c += V;
             ret += V;
             cap -= V;
             if(cap == ) break;
         }
     }
     if(cap > ) d[u] = -;
     return ret;
 }

 int Dinic(int u)
 {
     int ans = ;
     while(bfs())
     {
         memcpy(cur, head, sizeof(head));
         ans += dfs(u, INF);
     }
     return ans;
 }

 struct node
 {
     int u, v, flag, next;
 }Node[maxn << ];

 void add2(int u, int v)
 {
     Node[cnt2].u = u;
     Node[cnt2].v = v;
     Node[cnt2].next = head2[u];
     Node[cnt2].flag = ;
     head2[u] = cnt2++;
 }
 int used[maxn];
 void fleury(int u)
 {
     for(int i = head2[u]; i != -; i = Node[i].next)
     {
         if(!used[i])
         {
             used[i] = ;
             fleury(Node[i].v);
         }

     }
     st[cnt3++] = u;
 }

 void init()
 {
     mem(in, );
     mem(head, -);
     mem(out, );
     mem(st, );
     cnt = ;
     cnt2 = ;
     cnt3 = ;
     mem(head2, -);
     mem(used, );
     ss.clear();

 }

 char str[];

 int main()
 {
     int T;
     cin >> T;
     while(T--)
     {
         int u, v, w;
         cin >> n >> m;
         init();
         s = , t = maxn - ;
         for(int i = ; i <= m; i++)
         {
             scanf("%d%d%s", &u, &v, str);
             in[v]++, out[u]++;
             if(str[] == 'U') add(u, v, );
             else if(str[] == 'D') add2(u, v);
         }
         int flag = , m_sum = ;
         for(int i = ; i <= n; i++)
         {
             if(abs(out[i] - in[i]) & )
             {
                 flag = ;
                 break;
             }
             if(out[i] > in[i]) add(s, i, (out[i] - in[i]) / ), m_sum += (out[i] - in[i]) / ;
             else if(in[i] > out[i]) add(i, t, (in[i] - out[i]) / );

         }
         if(!flag && m_sum == Dinic(s))
         {
             for(int i = ; i < cnt; i++)
             {
                 if(!Edge[i].ff || Edge[i].u == s || Edge[i].v == t) continue;
                 if(Edge[i].c == ) add2(Edge[i].v, Edge[i].u);
                 else add2(Edge[i].u, Edge[i].v);
             }
             fleury();
             for(int i = cnt3 - ; i >= ; i--)
             {
                 if(i != cnt3 - ) printf(" ");
                 printf("%d", st[i]);
             }

             printf("\n");

         }
         else
             cout << "No euler circuit exist" << endl;
         if(T) printf("\n");

     }

     return ;
 }