求欧拉回路
圈套圈。该模板是uoj那道题的。
1 //#include<iostream> 2 #include<cstring> 3 #include<cstdio> 4 #include<time.h> 5 //#include<math.h> 6 //#include<set> 7 #include<queue> 8 //#include<bitset> 9 //#include<vector> 10 #include<algorithm> 11 #include<stdlib.h> 12 using namespace std; 13 14 #define LL long long 15 LL qread() 16 { 17 char c; LL s=0; int f=1; while ((c=getchar())<'0' || c>'9') (c=='-') && (f=-1); 18 do s=s*10+c-'0'; while ((c=getchar())>='0' && c<='9'); return s*f; 19 } 20 21 //Pay attention to '-' , LL and double of qread!!!! 22 23 int n,t,m; 24 #define maxn 100011 25 #define maxm 400011 26 struct Edge{int to,next;}edge[maxm]; int first[maxn],le=2; 27 void in(int x,int y) {Edge &e=edge[le]; e.to=y; e.next=first[x]; first[x]=le++;} 28 void insert(int x,int y) {in(x,y); in(y,x);} 29 30 //int ufs[maxn],size[maxn]; 31 //int find(int x) {return x==ufs[x]?x:(ufs[x]=find(ufs[x]));} 32 //void Union(int x,int y) {x=find(x); y=find(y); if (x!=y) ufs[x]=y,size[y]+=size[x];} 33 34 int du[maxn],indu[maxn],odu[maxn]; 35 36 int sta[maxm],top=0,boss; bool vis[maxm]; 37 void dfs(int x,int fa) 38 { 39 // cout<<x<<endl; 40 for (int &i=first[x];i;i=edge[i].next) 41 { 42 if ((i^1)==fa) continue; 43 if (~fa && vis[i>>1]) continue; 44 if (fa==-1 && vis[i]) continue; 45 int j=i; Edge &e=edge[j]; if (~fa) vis[j>>1]=1; else vis[j]=1; 46 if (e.to==boss) {if (~fa) sta[++top]=(j&1)?-(j>>1):(j>>1); else sta[++top]=j-1; boss=0; continue;} 47 if (boss==0) x=boss; 48 dfs(e.to,fa==-1?-1:j); if (~fa) sta[++top]=(j&1)?-(j>>1):(j>>1); else sta[++top]=j-1; 49 } 50 } 51 52 void solve1() 53 { 54 for (int i=1;i<=n;i++) if (du[i]&1) {puts("NO"); return;} 55 for (int i=1;i<=n;i++) if (du[i]) {dfs((boss=i),0); break;} 56 if (top!=m) {puts("NO"); return;} 57 puts("YES"); 58 for (int i=top;i;i--) printf("%d ",sta[i]); 59 } 60 61 void solve2() 62 { 63 for (int i=1;i<=n;i++) if (indu[i]!=odu[i]) {puts("NO"); return;} 64 for (int i=1;i<=n;i++) if (indu[i]) {dfs((boss=i),-1); break;} 65 if (top!=m) {puts("NO"); return;} 66 puts("YES"); 67 for (int i=top;i;i--) printf("%d ",sta[i]); 68 } 69 70 int main() 71 { 72 t=qread(); n=qread(); m=qread(); 73 if (m==0) {puts("YES"); return 0;} 74 for (int i=1,x,y;i<=m;i++) 75 {x=qread(); y=qread(); if (t==1) insert(x,y),du[x]++,du[y]++; else in(x,y),indu[y]++,odu[x]++;} 76 if (t==1) solve1(); else solve2(); 77 return 0; 78 }
顺便加个题51nod1967 路径定向
这可以用网络流，但T死。
实际把奇数度数点连起来做欧拉回路就好了。
