#include<cstdio> #include<algorithm> #include<cstring> #include<iostream> #include<cstdlib> #include<cmath> #include<vector> #include<map> #include<set> #include<queue> #include<bitset> using namespace std; typedef long long ll; typedef double db; const db pi=acos(-1); void gn(int &x){ int sg=1;char c;while(((c=getchar())<'0'||c>'9')&&c!='-'); if(c=='-')sg=-1,x=0;else x=c-'0'; while((c=getchar())>='0'&&c<='9')x=x*10+c-'0'; x*=sg; } void gn(ll &x){ int sg=1;char c;while(((c=getchar())<'0'||c>'9')&&c!='-'); if(c=='-')sg=-1,x=0;else x=c-'0'; while((c=getchar())>='0'&&c<='9')x=x*10+c-'0'; x*=sg; } int gcd(int a,int b){return b?gcd(b,a%b):a;} int n,m; //#define N 500005 #define N 1000005 #define M 1000005 struct edge{ int v,next; }e[M+N];int g[N*2];int etot=0; void ae(int u,int v){ e[etot].v=v;e[etot].next=g[u];g[u]=etot++; } int vis[N*2],ine[N*2],pre[N*2]; int cyfound=0; int cy[N*2],cylen=0; int oncy[N+M]; void fincy(int u){ vis[u]=1; for (int i=g[u];~i;i=e[i].next) if(vis[e[i].v]==0){ ine[e[i].v]=i; pre[e[i].v]=u; fincy(e[i].v); if(cyfound)return; }else if(vis[e[i].v]==1){ cyfound=1; int x=u; while(x!=e[i].v){ cy[++cylen]=x; oncy[ine[x]]=1; x=pre[x]; } cy[++cylen]=e[i].v; oncy[ine[e[i].v]=i]=1; for (int i=1;i<cylen-i+1;i++)swap(cy[i],cy[cylen-i+1]); return; } vis[u]=2; } int deg[N*2]={0}; int qu[N*2],p,q; int topo(){ for (int u=1;u<=2*n;u++) for (int i=g[u];~i;i=e[i].next)if(!oncy[i])deg[e[i].v]++; p=q=0; for (int u=1;u<=2*n;u++)if(deg[u]==0)qu[q++]=u; while(p!=q){ int u=qu[p++]; for (int i=g[u];~i;i=e[i].next)if(!oncy[i]){ deg[e[i].v]--; if(deg[e[i].v]==0)qu[q++]=e[i].v; } } if(q!=2*n)return 0; return 1; } int lef[N*2]={0},rig[N*2]={0}; int off[N+M]={0}; int main() { /*freopen("1.in","r",stdin); freopen("jc.out","w",stdout);*/ gn(n);gn(m); memset(g,-1,sizeof(g)); for (int i=1;i<=n;i++)ae(i,i+n); while(m--){ int x,y; gn(x);gn(y); ae(x+n,y); } for (int u=1;u<=2*n;u++)if(!vis[u]){ fincy(u); if(cyfound)break; } if(!cyfound){ printf("NIE\n"); return 0; } if(!topo()){ printf("0\n\n"); return 0; } for (int i=1;i<=cylen;i++)lef[cy[i]]=rig[cy[i]]=i; for (int j=2*n-1;j>=0;j--){ int u=qu[j]; if(!lef[u])lef[u]=1000000000; for (int i=g[u];~i;i=e[i].next)if(!oncy[i])lef[u]=min(lef[u],lef[e[i].v]); } for (int j=0;j<2*n;j++){ int u=qu[j]; for (int i=g[u];~i;i=e[i].next)if(!oncy[i])rig[e[i].v]=max(rig[e[i].v],rig[u]); } int r=cylen+1,l=0; for (int i=cylen;i>=1;i--)if(lef[cy[i]]<i)r=i; for (int i=1;i<=cylen;i++)if(rig[cy[i]]>i)l=i; if(l!=0){ for (int i=1;i<=l;i++)off[ine[cy[i]]]=1; for (int i=r+1;i<=cylen;i++)off[ine[cy[i]]]=1; } for (int i=1;i<=2*n;i++)rig[i]=0; for (int i=1;i<=cylen;i++)rig[cy[i]]=i; for (int j=2*n-1;j>=0;j--){ int u=qu[j]; for (int i=g[u];~i;i=e[i].next)if(!oncy[i])rig[u]=max(rig[u],rig[e[i].v]); } int far=0; for (int i=1;i<=cylen;i++)if(rig[cy[i]]>far){ for (int j=max(i,far)+1;j<=rig[cy[i]];j++)off[ine[cy[j]]]=1; far=rig[cy[i]]; } int cnt=0; for (int i=0;i<n;i++)if(oncy[i] && !off[i])cnt++; printf("%d\n",cnt); for (int i=0;i<n;i++)if(oncy[i] && !off[i]){ printf("%d ",i+1); } printf("\n"); return 0; }
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 | #include<cstdio> #include<algorithm> #include<cstring> #include<iostream> #include<cstdlib> #include<cmath> #include<vector> #include<map> #include<set> #include<queue> #include<bitset> using namespace std; typedef long long ll; typedef double db; const db pi=acos(-1); void gn(int &x){ int sg=1;char c;while(((c=getchar())<'0'||c>'9')&&c!='-'); if(c=='-')sg=-1,x=0;else x=c-'0'; while((c=getchar())>='0'&&c<='9')x=x*10+c-'0'; x*=sg; } void gn(ll &x){ int sg=1;char c;while(((c=getchar())<'0'||c>'9')&&c!='-'); if(c=='-')sg=-1,x=0;else x=c-'0'; while((c=getchar())>='0'&&c<='9')x=x*10+c-'0'; x*=sg; } int gcd(int a,int b){return b?gcd(b,a%b):a;} int n,m; //#define N 500005 #define N 1000005 #define M 1000005 struct edge{ int v,next; }e[M+N];int g[N*2];int etot=0; void ae(int u,int v){ e[etot].v=v;e[etot].next=g[u];g[u]=etot++; } int vis[N*2],ine[N*2],pre[N*2]; int cyfound=0; int cy[N*2],cylen=0; int oncy[N+M]; void fincy(int u){ vis[u]=1; for (int i=g[u];~i;i=e[i].next) if(vis[e[i].v]==0){ ine[e[i].v]=i; pre[e[i].v]=u; fincy(e[i].v); if(cyfound)return; }else if(vis[e[i].v]==1){ cyfound=1; int x=u; while(x!=e[i].v){ cy[++cylen]=x; oncy[ine[x]]=1; x=pre[x]; } cy[++cylen]=e[i].v; oncy[ine[e[i].v]=i]=1; for (int i=1;i<cylen-i+1;i++)swap(cy[i],cy[cylen-i+1]); return; } vis[u]=2; } int deg[N*2]={0}; int qu[N*2],p,q; int topo(){ for (int u=1;u<=2*n;u++) for (int i=g[u];~i;i=e[i].next)if(!oncy[i])deg[e[i].v]++; p=q=0; for (int u=1;u<=2*n;u++)if(deg[u]==0)qu[q++]=u; while(p!=q){ int u=qu[p++]; for (int i=g[u];~i;i=e[i].next)if(!oncy[i]){ deg[e[i].v]--; if(deg[e[i].v]==0)qu[q++]=e[i].v; } } if(q!=2*n)return 0; return 1; } int lef[N*2]={0},rig[N*2]={0}; int off[N+M]={0}; int main() { /*freopen("1.in","r",stdin); freopen("jc.out","w",stdout);*/ gn(n);gn(m); memset(g,-1,sizeof(g)); for (int i=1;i<=n;i++)ae(i,i+n); while(m--){ int x,y; gn(x);gn(y); ae(x+n,y); } for (int u=1;u<=2*n;u++)if(!vis[u]){ fincy(u); if(cyfound)break; } if(!cyfound){ printf("NIE\n"); return 0; } if(!topo()){ printf("0\n\n"); return 0; } for (int i=1;i<=cylen;i++)lef[cy[i]]=rig[cy[i]]=i; for (int j=2*n-1;j>=0;j--){ int u=qu[j]; if(!lef[u])lef[u]=1000000000; for (int i=g[u];~i;i=e[i].next)if(!oncy[i])lef[u]=min(lef[u],lef[e[i].v]); } for (int j=0;j<2*n;j++){ int u=qu[j]; for (int i=g[u];~i;i=e[i].next)if(!oncy[i])rig[e[i].v]=max(rig[e[i].v],rig[u]); } int r=cylen+1,l=0; for (int i=cylen;i>=1;i--)if(lef[cy[i]]<i)r=i; for (int i=1;i<=cylen;i++)if(rig[cy[i]]>i)l=i; if(l!=0){ for (int i=1;i<=l;i++)off[ine[cy[i]]]=1; for (int i=r+1;i<=cylen;i++)off[ine[cy[i]]]=1; } for (int i=1;i<=2*n;i++)rig[i]=0; for (int i=1;i<=cylen;i++)rig[cy[i]]=i; for (int j=2*n-1;j>=0;j--){ int u=qu[j]; for (int i=g[u];~i;i=e[i].next)if(!oncy[i])rig[u]=max(rig[u],rig[e[i].v]); } int far=0; for (int i=1;i<=cylen;i++)if(rig[cy[i]]>far){ for (int j=max(i,far)+1;j<=rig[cy[i]];j++)off[ine[cy[j]]]=1; far=rig[cy[i]]; } int cnt=0; for (int i=0;i<n;i++)if(oncy[i] && !off[i])cnt++; printf("%d\n",cnt); for (int i=0;i<n;i++)if(oncy[i] && !off[i]){ printf("%d ",i+1); } printf("\n"); return 0; } |