题意：见原题面
一圈圈剥叶子，剥 k/2 层即可。
考场上脑残觉得这玩意得写数据结构维护区间染色...
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#include <cmath> #include <queue> #include <cstdio> #include <iomanip> #include <cstdlib> #include <cstring> #include <iostream> #include <algorithm> #define N 1000005 #define ll long long using namespace std; char xB[1<<15],*xS=xB,*xT=xB; #define getchar() (xS==xT&&(xT=(xS=xB)+fread(xB,1,1<<15,stdin),xS==xT)?0:*xS++) 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*10+ch-'0';ch=getchar();} return x*f; } int n,k; struct zgz { int next,to; }edge[N<<1]; int head[N],cnt=1; void add(int from,int to) { edge[cnt].to=to; edge[cnt].next=head[from]; head[from]=cnt++; } int dep[N],deg[N],ans; queue<int> q; int main() { n=read(),k=read(); if(k==1||n==1) { puts("1"); return 0; } for(int i=1;i<=n-1;i++) { int x=read(),y=read(); deg[x]++,deg[y]++; add(x,y),add(y,x); } for(int i=1;i<=n;i++) if(deg[i]==1)q.push(i),dep[i]=1,ans++; while(!q.empty()) { int x=q.front();q.pop(); for(int i=head[x];i;i=edge[i].next) { int to=edge[i].to; deg[to]--; if(deg[to]==1&&dep[x]!=k/2) { q.push(to); dep[to]=dep[x]+1; ans++; } } } if(k&1) { for(int i=1;i<=n;i++) if(!dep[i]) { printf("%d\n",ans+1); return 0; } } printf("%d\n",ans); } |
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