[BZOJ1064][Noi2008]假面舞会

来源：互联网发布：淘宝二手市场怎么进入编辑：程序博客网时间：2024/04/28 14:44

原题地址

OLZ BYVOID神犇题解:
https://www.byvoid.com/blog/noi-2008-party/

顶点标号的技巧很巧妙OLZ

AC code:

#include <cstdio>const int N=100010;const int M=1000010;int  n,m,cnt=1,tot,cb,top;int  head[N],num[N],a[N],bl[N],stk[N],minn[N],maxn[N];bool ins[N];struct Edge{    int u,v,w,next;    Edge() {}    Edge(int u,int v,int w,int next):u(u),v(v),w(w),next(next) {}}E[M];int Abs(int x){    return x<0?-x:x;}int gcd(int x,int y){    return y?gcd(y,x%y):x;}int Max(int x,int y){    return x>y?x:y;}int Min(int x,int y){    return x<y?x:y;}void addedge(int u,int v){    E[++cnt]=Edge(u,v,1,head[u]);    E[++cnt]=Edge(v,u,-1,head[v]);    head[u]=cnt-1;head[v]=cnt;}void read(){    scanf("%d%d",&n,&m);    for(int i=1;i<=m;i++){        int u,v;        scanf("%d%d",&u,&v);        addedge(u,v);    }}void DFS(int x,int cnum){    num[x]=cnum;bl[x]=cb;ins[x]=1;stk[++top]=x;    for(int i=head[x];i;i=E[i].next){        if(bl[E[i].v]){            if(ins[E[i].v]&&stk[top-1]!=E[i].v&&cnum+E[i].w-num[E[i].v])                a[++tot]=Abs(cnum+E[i].w-num[E[i].v]);            continue ;        }        DFS(E[i].v,cnum+E[i].w);        ins[E[i].v]=0;top--;    }}int main(){    read();    for(int i=1;i<=n;i++){        if(!bl[i]){            cb++;            DFS(i,1);        }    }    if(tot){        int ans=a[1];        for(int i=2;i<=tot;i++) ans=gcd(ans,a[i]);        if(ans<3) printf("-1 -1\n");        else{            for(int i=3;i<=ans;i++){                if(!(ans%i)){                    printf("%d %d\n",ans,i);                    break;                }            }        }    }    else{        int ans=0;        for(int i=1;i<=n;i++) minn[i]=1<<28;        for(int i=1;i<=n;i++){            minn[bl[i]]=Min(minn[bl[i]],num[i]);            maxn[bl[i]]=Max(maxn[bl[i]],num[i]);        }        for(int i=1;i<=n;i++) if(maxn[i]) ans+=maxn[i]-minn[i]+1;        if(ans<3) printf("-1 -1\n");        else printf("%d 3\n",ans);    }    return 0;}

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