Leaf Sets CodeForces - 1042F (树,最小划分)

大意: 给定树, 求叶子的最小划分, 使得每个划分内任意两个叶子距离不超过k.

任选一个非叶结点, 贪心合并.

#include <iostream>
#include <sstream>
#include <algorithm>
#include <cstdio>
#include <math.h>
#include <set>
#include <map>
#include <queue>
#include <string>
#include <string.h>
#include <bitset>
#define REP(i,a,n) for(int i=a;i<=n;++i)
#define PER(i,a,n) for(int i=n;i>=a;--i)
#define hr putchar(10)
#define pb push_back
#define lc (o<<1)
#define rc (lc|1)
#define mid ((l+r)>>1)
#define ls lc,l,mid
#define rs rc,mid+1,r
#define x first
#define y second
#define io std::ios::sync_with_stdio(false)
#define endl '\n'
#define DB(a) ({REP(__i,1,n) cout<<a[__i]<<' ';hr;})
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int P = 1e9+7, P2 = 998244353, INF = 0x3f3f3f3f;
ll gcd(ll a,ll b) {return b?gcd(b,a%b):a;}
ll qpow(ll a,ll n) {ll r=1%P;for (a%=P;n;a=a*a%P,n>>=1)if(n&1)r=r*a%P;return r;}
ll inv(ll x){return x<=1?1:inv(P%x)*(P-P/x)%P;}
inline int rd() {int x=0;char p=getchar();while(p<'0'||p>'9')p=getchar();while(p>='0'&&p<='9')x=x*10+p-'0',p=getchar();return x;}
//head

#ifdef ONLINE_JUDGE
const int N = 1e6+10;
#else
const int N = 111;
#endif

int n, k, ans;
vector<int> g[N];

int dfs(int x, int f) {
	if (g[x].size()==1) return 0;
	vector<int> v;
	for (int y:g[x]) if (y!=f) v.pb(dfs(y,x)+1);
	sort(v.begin(),v.end());
	int sz = v.size()-1;
	for (; sz>=1; --sz) {
		if (v[sz]+v[sz-1]<=k) break;
		++ans;
	}
	return v[sz];
}

int main() {
	scanf("%d%d", &n, &k);
	REP(i,2,n) {
		int u, v;
		scanf("%d%d", &u, &v);
		g[u].pb(v),g[v].pb(u);
	}
	int rt = 1;
	PER(i,1,n) if (g[i].size()>1) rt=i;
	dfs(rt,0);
	printf("%d\n",ans+1);
}