Codeforces Round #375 (Div. 2)E. One-Way Reform

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstdlib>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <cstring>
 7 #include <stack>
 8 #include <cctype>
 9 #include <queue>
10 #include <string>
11 #include <vector>
12 #include <set>
13 #include <map>
14 #include <climits>
15 #define lson rt<<1,l,mid
16 #define rson rt<<1|1,mid+1,r
17 #define fi first
18 #define se second
19 #define ping(x,y) ((x-y)*(x-y))
20 #define mst(x,y) memset(x,y,sizeof(x))
21 #define mcp(x,y) memcpy(x,y,sizeof(y))
22 using namespace std;
23 #define gamma 0.5772156649015328606065120
24 #define MOD 1000000007
25 #define inf 0x3f3f3f3f
26 #define N 50005
27 #define maxn 30010
28 typedef pair<int,int> PII;
29 typedef long long LL;
30 LL read(){
31     LL x=0,f=1;char ch=getchar();
32     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
33     while(ch>=‘0‘&&ch<=‘9‘){x=(x<<3)+(x<<1)+ch-‘0‘;ch=getchar();}
34     return x*f;
35 }
36 
37 int n,m,k,ans,in[205];
38 int vis[205][205];
39 set<int>S[205];
40 vector<PII >V;
41 void dfs(int u){
42     while(S[u].size()){
43         int x=*S[u].begin();S[u].erase(S[u].begin());
44         if(vis[u][x])continue;
45         vis[u][x]=vis[x][u]=1;
46         V.push_back(make_pair(u,x));
47         dfs(x);
48     }
49 }
50 int main(){
51     int i,j,group,x,y,v,Case=0;
52     group=read();
53     while(group--){
54         n=read(),m=read();
55         mst(in,0);V.clear();
56         mst(vis,0);
57         for(i=0;i<=n;++i) S[i].clear();
58         for(i=1;i<=m;++i){
59             x=read(),y=read();
60             S[x].insert(y),S[y].insert(x);
61             ++in[x],++in[y];
62         }
63         int ans=n;
64         for(i=1;i<=n;++i)if(in[i]&1){
65             --ans;
66             S[0].insert(i),S[i].insert(0);
67         }
68         for(i=1;i<=n;++i)
69             if(S[i].size())
70                 dfs(i);
71         printf("%d\n",ans);
72         for(PII u:V)if(u.fi!=0&&u.se!=0){
73             printf("%d %d\n",u.fi,u.se);
74         }
75     }
76     return 0;
77 }