Vijos 1523 贪吃的九头龙 【树形DP】

8 2 4
1 2 20
1 3 4
1 4 13
2 5 10
2 6 12
3 7 15
3 8 5

4

 1 /****************************************************
2
3     Author : Coolxxx
4     Copyright 2017 by Coolxxx. All rights reserved.
5     BLOG : http://blog.csdn.net/u010568270 6
7 ****************************************************/
8 #include<bits/stdc++.h>
9 #pragma comment(linker,"/STACK:1024000000,1024000000")
10 #define abs(a) ((a)>0?(a):(-(a)))
11 #define lowbit(a) (a&(-a))
12 #define sqr(a) ((a)*(a))
13 #define mem(a,b) memset(a,b,sizeof(a))
14 #define eps (1e-8)
15 #define J 10000
16 #define mod 1000000007
17 #define MAX 0x7f7f7f7f
18 #define PI 3.14159265358979323
19 #define N 30420 using namespace std;
21 typedef long long LL;
22 double anss;
23 LL aans;
24 int cas,cass;
25 int n,m,lll,ans;
26 int l
,r
,q
,s
,fa
;
27 int ma

;
28 int f

[2];
29 void dfs(int now,int ff)
30 {
31     if(!now)return;
32     fa[now]=ff;
33     if(l[now])dfs(l[now],now);
34     if(r[now])dfs(r[now],now);
35     s[now]=s[l[now]]+s[r[now]]+1;
36     q[++lll]=now;
37 }
38 int main()
39 {
40     #ifndef ONLINE_JUDGE
41     freopen("1.txt","r",stdin);
42 //    freopen("2.txt","w",stdout);
43     #endif
44     int i,j,k;
45     int x,y,z;
46 //    for(scanf("%d",&cass);cass;cass--)
47 //    for(scanf("%d",&cas),cass=1;cass<=cas;cass++)
48 //    while(~scanf("%s",s))
49     while(~scanf("%d",&n))
50     {
51         mem(l,0);mem(r,0);mem(f,1);
52         scanf("%d%d",&m,&cas);
53         cass=(m==2);
54         for(i=1;i<n;i++)
55         {
56             scanf("%d%d%d",&x,&y,&z);
57             if(x>y)swap(x,y);
58             if(!l[x])
59             {
60                 l[x]=y;
61                 ma[x][y]=ma[y][x]=z;
62             }
63             else
64             {
65                 r[y]=l[x];
66                 l[x]=y;
67                 ma[x][y]=ma[y][x]=z;
68                 ma[y][r[y]]=ma[r[y]][y]=ma[x][r[y]];
69             }
70         }
71         if(m+cas>n){puts("-1");continue;}
72         lll=0;
73         dfs(1,0);
74         f[0][0][0]=f[0][0][1]=0;
75         for(x=1;x<=lll;x++)
76         {
77             i=q[x];
78             for(j=0;j<=min(cas,s[i]);j++)
79             {
80                 for(y=0;y<=j;y++)
81                 {
82                     for(k=0;k<=1;k++)
83                     {
84                         f[i][j][k]=min(f[i][j][k],f[l[i]][y][0]+f[r[i]][j-y][k]+ma[i][fa[i]]*(k==0)*cass);
85                         if(y>0)f[i][j][k]=min(f[i][j][k],f[l[i]][y-1][1]+f[r[i]][j-y][k]+ma[i][fa[i]]*(k==1));
86                     }
87                 }
88             }
89         }
90         printf("%d\n",f[l[1]][cas-1][1]);
91     }
92     return 0;
93 }
94 /*
95 //
96
97 //
98 */