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| #include <bits/stdc++.h> #define MAXN 100005 using namespace std; inline int read(){ int x=0,f=1; char ch=getchar(); while (ch<'0'||ch>'9'){ if (ch=='-') f=-1; ch=getchar(); } while (ch>='0'&&ch<='9'){ x=(x<<3)+(x<<1)+(ch^'0'); ch=getchar(); } return x*f; } int n,m,k; namespace DFZ{ vector<int>G[MAXN]; void AddEdge(int u,int v){ G[u].push_back(v); } int sz[MAXN],Max[MAXN],centre; int vis[MAXN]; void Find(int u,int father,int treesz){ sz[u]=1,Max[u]=0; for (int i=0;i<G[u].size();++i){ int v=G[u][i]; if (v&&v!=father&&!vis[v]){ Find(v,u,treesz); sz[u]+=sz[v]; Max[u]=max(Max[u],sz[v]); } } int up=treesz-sz[u]; Max[u]=max(Max[u],up); if (Max[u]<Max[centre]) centre=u; } int stk[MAXN],top; void Koko(int u,int father,int dep){ stk[++top]=dep; for (int i=0;i<G[u].size();++i){ int v=G[u][i]; if (v&&v!=father&&!vis[v]) Koko(v,u,dep+1); } } long long Calc(int u,int w){ top=0; Koko(u,0,w); sort(stk+1,stk+1+top); long long ans=0; for (int i=1;i<=top;++i){ int pos=lower_bound(stk+1,stk+1+top,k-stk[i]-1)-stk-1; ans+=top-pos; } return ans; } long long ret=0; int GetCentre(int u,int sz){ centre=0; Find(u,0,sz); return centre; } void dfs(int u){ vis[u]=true; ret+=Calc(u,0); for (int i=0;i<G[u].size();++i){ int v=G[u][i]; if (v&&!vis[v]){ ret-=Calc(v,1); dfs(GetCentre(v,sz[v])); } } } } using namespace DFZ; void SolveTree(){ dfs(GetCentre(1,n)); printf("%lld\n",ret/2ll); } bool flag; int fa[MAXN],U,V,t; void FindCircle(int u,int father){ if (flag) return ; fa[u]=father; if (vis[u]){ t=u; flag=true; return ; } vis[u]=true; for (register int i=0;i<G[u].size();++i){ int v=G[u][i]; if (v==father) continue; FindCircle(v,u); } } vector<int>Circle; namespace BIT{ int C[MAXN*2]; #define lowbit(i) i&(-i) void Add(int k,int val){ k+=MAXN; for (int i=k;i>0;i-=lowbit(i)) C[i]+=val; } int Ask(int k){ k+=MAXN; int ans=0; for (int i=k;i<MAXN*2;i+=lowbit(i)) ans+=C[i]; return ans; } } using namespace BIT; int Mark[MAXN];
void QuerySubtree(int u,int father,int w){ ret+=Ask(k-w-1); for (int i=0;i<G[u].size();++i){ int v=G[u][i]; if (v&&v!=father&&!Mark[v]) QuerySubtree(v,u,w+1); } } void AddSubtree(int u,int father,int w){ Add(w,1); for (int i=0;i<G[u].size();++i){ int v=G[u][i]; if (v&&v!=father&&!Mark[v]) AddSubtree(v,u,w+1); } } void SolveJHTree(){ FindCircle(1,1); memset(vis,0,sizeof(vis)); U=t,V=fa[t]; for (int i=0;i<G[U].size();++i) if (G[U][i]==V) G[U][i]=0; for (int i=0;i<G[V].size();++i) if (G[V][i]==U) G[V][i]=0; dfs(GetCentre(U,n)); ret/=2ll; int u=t; while (true){ u=fa[u]; Circle.push_back(u); if (u==t) break; } for (int i=0;i<Circle.size();++i) Mark[Circle[i]]=true; for (int i=0;i<Circle.size();++i){ u=Circle[i]; QuerySubtree(u,0,Circle.size()-i-1); AddSubtree(u,0,i+1); } printf("%lld\n",ret); } int main(){ n=read(),m=read(),k=read(); for (int i=1;i<=m;++i){ int u=read(),v=read(); AddEdge(u,v); AddEdge(v,u); } Max[0]=0x7fffffff; if (m==n-1) SolveTree(); else SolveJHTree(); }
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