题目链接：http://www.lydsy.com/JudgeOnline/problem.php?id=3779
丰富下博客的文章
其实是看着commonc学长的题解写的
我就不说什么了つ﹏⊂ 学长讲的非常棒
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#include<bits/stdc++.h> #define MAXN 100010 typedef double db; using namespace std; inline unsigned int rd(){ unsigned int x=0,y=1;char c=getchar(); while(!isdigit(c)){if(c=='-')y=-y;c=getchar();} while(isdigit(c))x=x*10+c-'0',c=getchar(); return x*y; } struct node{ unsigned int l,r,len; unsigned int sum,lazy; }tree[MAXN*4]; unsigned int n,m; vector<unsigned int>v[MAXN]; unsigned int sz[MAXN],hson[MAXN],ffa[MAXN],deep[MAXN],tp[MAXN],tot,dfn[MAXN],fan[MAXN]; unsigned int fa[MAXN],son[MAXN][2],L[MAXN],R[MAXN],root=1,rev[MAXN]; void dfs1(unsigned int x){ sz[x]=1; for(unsigned int i=0; i<v[x].size(); i++){ unsigned int to=v[x][i]; if(to==fa[x])continue; deep[to]=deep[x]+1; ffa[to]=fa[to]=x; dfs1(to); sz[x]+=sz[to]; if(sz[to]>sz[hson[x]])hson[x]=to; } } void dfs2(unsigned int x,unsigned int tt){ tot++; dfn[x]=tot; fan[tot]=x; tp[x]=tt; if(hson[x])dfs2(hson[x],tt); for(unsigned int i=0; i<v[x].size(); i++){ unsigned int to=v[x][i]; if(to==fa[x] || to==hson[x])continue; dfs2(to,to); } } inline void pushup1(unsigned int x){ tree[x].sum=tree[x*2].sum+tree[x*2+1].sum; } inline void pushdown1(unsigned int x){ if(!tree[x].lazy)return; tree[x*2].lazy+=tree[x].lazy; tree[x*2+1].lazy+=tree[x].lazy; tree[x*2].sum+=tree[x*2].len*tree[x].lazy; tree[x*2+1].sum+=tree[x*2+1].len*tree[x].lazy; tree[x].lazy=0; } void build(unsigned int x,unsigned int l,unsigned int r){ tree[x].l=l; tree[x].r=r; tree[x].len=r-l+1; if(l==r){ tree[x].sum=deep[fan[l]]; return; } unsigned int mid=(l+r)/2; build(x*2,l,mid); build(x*2+1,mid+1,r); pushup1(x); } unsigned int Get(unsigned int x,unsigned int y){ while(tp[x]!=tp[y]){ if(ffa[tp[y]]==x)return tp[y]; y=ffa[tp[y]]; } return fan[dfn[x]+1]; } void change(unsigned int x,unsigned int l,unsigned int r,unsigned int k){ if(tree[x].l==l && tree[x].r==r){ tree[x].lazy+=k; tree[x].sum+=tree[x].len*k; return; } pushdown1(x); unsigned int mid=(tree[x].l+tree[x].r)/2; if(r<=mid)change(x*2,l,r,k); else if(l>mid)change(x*2+1,l,r,k); else change(x*2,l,mid,k),change(x*2+1,mid+1,r,k); pushup1(x); } void Change(unsigned int x,unsigned int k){ if(x==root)change(1,1,n,k); else if(dfn[x]<=dfn[root] && dfn[x]+sz[x]>=dfn[root]+sz[root]){ x=Get(x,root); if(dfn[x]>1)change(1,1,dfn[x]-1,k); if(dfn[x]+sz[x]-1<n)change(1,dfn[x]+sz[x],n,k); } else change(1,dfn[x],dfn[x]+sz[x]-1,k); } void pushup(unsigned int x){ if(!son[x][0])L[x]=x; else L[x]=L[son[x][0]]; if(!son[x][1])R[x]=x; else R[x]=R[son[x][1]]; } void Rev(unsigned int x){ if(!x)return; swap(son[x][0],son[x][1]); swap(L[x],R[x]); rev[x]^=1; } void pushdown(unsigned int x){ if(rev[x]){ Rev(son[x][0]); Rev(son[x][1]); rev[x]=false; } } bool isroot(unsigned int x){ return son[fa[x]][0]!=x && son[fa[x]][1]!=x; } inline bool is_right(unsigned int x){ return son[fa[x]][1]==x; } inline void Rotate(unsigned int x){ unsigned int f=fa[x],ff=fa[f],which=is_right(x); if(!isroot(f))son[ff][son[ff][1]==f]=x; son[f][which]=son[x][which^1]; fa[son[f][which]]=f;fa[f]=x; son[x][which^1]=f;fa[x]=ff; pushup(f);pushup(x); } void getdown(unsigned int x){ if(!isroot(x))getdown(fa[x]); pushdown(x); } inline void splay(unsigned int x){ getdown(x); while(!isroot(x)){ unsigned int f=fa[x]; if(!isroot(f))Rotate((is_right(x)==is_right(f)?f:x)); Rotate(x); } } void access(unsigned int x){ unsigned int t=0; while(x){ splay(x); if(son[x][1])Change(L[son[x][1]],1); son[x][1]=t; if(t)Change(L[t],-1); pushup(x); t=x; x=fa[x]; } } void makeroot(unsigned int x){ access(x); splay(x); swap(son[x][0],son[x][1]); swap(L[x],R[x]); rev[x]^=1; } unsigned int query(unsigned int x,unsigned int l,unsigned int r){ if(tree[x].l==l && tree[x].r==r)return (unsigned int)tree[x].sum; pushdown1(x); unsigned int mid=(tree[x].l+tree[x].r)/2; if(r<=mid)return query(x*2,l,r); else if(l>mid)return query(x*2+1,l,r); else return query(x*2,l,mid)+query(x*2+1,mid+1,r); } db Query(unsigned int x){ db ret=0; if(x==root)return query(1,1,n)*1.0/n; else if(dfn[x]<=dfn[root] && dfn[x]+sz[x]>=dfn[root]+sz[root]){ x=Get(x,root); if(dfn[x]>1)ret+=query(1,1,dfn[x]-1); if(dfn[x]+sz[x]-1<n)ret+=query(1,dfn[x]+sz[x],n); return ret*1.0/(n-sz[x]); } else return query(1,dfn[x],dfn[x]+sz[x]-1)*1.0/sz[x]; } int main(){ unsigned int i,x,y; n=rd(),m=rd(); for(i=1; i<n; i++){ x=rd(),y=rd(); v[x].push_back(y); v[y].push_back(x); } dfs1(1); dfs2(1,1); for(i=1; i<=n; i++)L[i]=R[i]=i; build(1,1,n); char op[21]; while(m--){ scanf("%s",op); x=rd(); if(op[2]=='L')access(x); else if(op[2]=='C')makeroot(x),root=x; else printf("%.10lf\n",Query(x)+1.0); } return 0; } |
