http://acm.hdu.edu.cn/showproblem.php?pid=1520
类型：树dp简单题
AC Code
1 #include <cstdio> 2 #include <cstring> 3 #include <algorithm> 4 using namespace std; 5 #define maxn 6005 6 struct node{ 7 int y,next; 8 }ee[maxn<<1]; 9 int link[maxn],t; 10 int f[maxn],g[maxn],val[maxn]; 11 void maketree(int a,int b) 12 { 13 ee[++t].y=a; 14 ee[t].next=link[b]; 15 link[b]=t; 16 } 17 void dfs(int root,int father) 18 { 19 for(int i=link[root];i;i=ee[i].next){ 20 if(ee[i].y!=father){ 21 dfs(ee[i].y,root); 22 f[root]+=g[ee[i].y]; 23 g[root]+=max(g[ee[i].y],f[ee[i].y]); 24 } 25 } 26 f[root]+=val[root]; 27 } 28 int main() 29 { 30 int n,a,b; 31 while(~scanf("%d",&n)){ 32 t=0; 33 for(int i=1;i<=n;i++) 34 scanf("%d",val+i); 35 memset(link,0,sizeof(link)); 36 while(scanf("%d%d",&a,&b)&&(a||b)){ 37 maketree(a,b); 38 maketree(b,a); 39 } 40 memset(f,0,sizeof(f)); 41 memset(g,0,sizeof(g)); 42 dfs(1,1); 43 printf("%d\n",max(f[1],g[1])); 44 } 45 return 0; 46 }