【BZOJ4813】 [Cqoi2017]小Q的棋盘

#include <bits/stdc++.h>
#define N 109
using namespace std;
int n,m,number,first
,x,y,size
,deep
,Max;
struct edge
{
int to,next;
void add(int x,int y)
{
to=y,next=first[x],first[x]=number;
}
}e[N<<1];
void dfs(int x,int fa)
{
size[x]=1;
deep[x]=deep[fa]+1;
if (deep[x]>deep[Max]) Max=x;
for (int i=first[x];i;i=e[i].next)
if (e[i].to!=fa)
{
dfs(e[i].to,x);
size[x]+=size[e[i].to];
}
}
int main()
{
scanf("%d%d",&n,&m);
for (int i=1;i<n;i++)
{
scanf("%d%d",&x,&y);
x++,y++;
e[++number].add(x,y),e[++number].add(y,x);
}
dfs(1,0);
if (deep[Max]>m) printf("%d\n",m+1);
else
if (deep[Max]+(n-deep[Max]-1)*2<=m)
printf("%d\n",n);
else printf("%d\n",deep[Max]+(m-deep[Max])/2+1);
return 0;
}