#include<bits/stdc++.h>
#define RG register
#define IL inline
#define _ 500005
#define INF 1e18
#define ll long long
using namespace std;
IL ll gi(){
RG ll data = 0 , m = 1; RG char ch = 0;
while(ch != '-' && (ch<'0' || ch > '9')) ch = getchar();
if(ch == '-'){m = 0; ch = getchar();}
while(ch>='0' && ch<='9'){data = (data<<1) + (data<<3) + ch - '0' ; ch = getchar();}
return (m) ? data : -data ;
}
struct DP{
ll v , cnt ;
IL DP(){cnt = v = 0 ; }
IL DP(RG ll a , RG ll b){v = a ; cnt = b ; }
IL void mem(){cnt = v = 0 ; }
DP operator + (RG DP &B){return DP(v + B.v , cnt + B.cnt) ; }
DP operator + (RG ll &B){return DP(v + B , cnt) ; }
DP operator * (RG DP &B){return DP(v + B.v , cnt + B.cnt - 1) ; }
}f[_][3],Ans[_],tmp;
IL DP Max(RG DP A , RG DP B){
if(A.v ^ B.v) return (A.v < B.v) ? B : A ;
else return (A.cnt < B.cnt) ? B : A ;
}
ll n,K,L,R,C,Ret,head[_]; struct Edge{ll to,next,w;}t[_<<2] ; ll oo ;
IL void add(RG ll u,RG ll v,RG ll w){
t[++oo] = (Edge){v , head[u] , w} ; head[u] = oo ;
t[++oo] = (Edge){u , head[v] , w} ; head[v] = oo ;
}
void dfs(RG ll u,RG ll From){
f[u][0] = (DP){0 , 0} ; Ans[u] = (DP){-INF , 0} ;
f[u][1] = (DP){-C , 1} ; f[u][2] = (DP){-INF , 0} ;
for(RG ll i = head[u] ; i ; i = t[i].next){
RG ll v = t[i].to ; if(v == From) continue ;
dfs(v , u) ;
f[u][2] = Max(f[u][2] , f[u][2] + Ans[v]) ;
f[u][2] = Max(f[u][2] , (f[u][1] * f[v][1]) + t[i].w + C) ;
tmp = f[u][0] + f[v][0]; C = -C ; tmp = tmp + t[i].w + C; C = -C ; tmp.cnt ++ ;
f[u][1] = Max(f[u][1] , f[u][1] + Ans[v]) ;
f[u][1] = Max(f[u][1] , Max(f[u][0] + f[v][1] + t[i].w , tmp)) ;
f[u][0] = Max(f[u][0] , f[u][0] + Ans[v]) ;
}
Ans[u] = Max(Max(f[u][0] , f[u][1]) , f[u][2]) ; return ;
}
int main(){
n = gi() ; K = gi() ;
for(RG ll i = 1,u,v,w; i < n; i ++)
u = gi() , v = gi() , w = gi() , add(u , v , w) , R = R + abs(w);
++ K ; L = -R ;
while(L <= R){
C = (L + R) >> 1 ;
dfs(1 , 0) ;
if(Ans[1].cnt <= K) Ret = C , R = C - 1 ;
else L = C + 1;
}
C = Ret ; dfs(1 , 0) ;
printf("%lld\n" , Ans[1].v + Ret * Ans[1].cnt) ; return 0 ;
}
原文地址:https://www.cnblogs.com/Guess2/p/9051429.html
时间: 2024-11-06 03:50:59