hdu1520 Anniversary party basic tree dp

Title link: http://acm.hdu.edu.cn/showproblem.php?pid=1520

The general idea is to give a membership tree, each person represents a node, each node has a value, and only one pair of points with a parent-child relationship can be selected, asking how to maximize the sum of the weights.

code show as below:

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 typedef unsigned int ui;
 4 typedef long long ll;
 5 typedef unsigned long long ull;
 6 #define pf printf
 7 #define mem(a,b) memset(a,b,sizeof(a))
 8 #define prime1 1e9+7
 9 #define prime2 1e9+9
10 #define pi 3.14159265
11 #define lson l,mid,rt<<1
12 #define rson mid+1,r,rt<<1|1
13 #define scand(x) scanf("%llf",&x) 
14 #define f(i,a,b) for(int i=a;i<=b;i++)
15 #define scan(a) scanf("%d",&a)
16 #define mp(a,b) make_pair((a),(b))
17 #define P pair<int,int>
18 #define dbg(args) cout<<#args<<":"<<args<<endl;
19 #define inf 0x7ffffff
20 inline int read(){
21     int ans=0,w=1;
22     char ch=getchar();
23     while(!isdigit(ch)){if(ch == ' - ' ) w = -1 ; ch = getchar ();)
 24      while (isdigit (ch)) ans = (ans << 3 ) + (ans << 1 ) + ch- ' 0 ' , ch = getchar ();
 25      return ans * w;
 26  }
 27  int n, m, t;
 28  const  int maxn = 1e4 + 10 ;
 29  int value [maxn];
 30  int dp [maxn] [ 2 ]; // 0 Indicates the maximum weight sum not selected at this point, 1 indicates the maximum weight sum selected at this point and 
31 vector < int> G [maxn];
 32  int f [maxn]; // The setting of f is to find the root node 
33  void dfs ( int u)
 34  {
 35      dp [u] [ 0 ] = 0 ;
 36      dp [u] [ 1 ] = value [u]; // Initial value setting 
for both participation and non-participation 37      for ( int i = 0 ; i <G [u] .size (); i ++ )
 38      {
 39          int son = G [u] [i];
 40          dfs (son); // Dfs 
41          dp [u] [ 0] + = max (dp [son] [ 1 ], dp [son] [ 0 ]); // After the parent node is not selected, the child node can be optional 
42          dp [u] [ 1 ] + = dp [son] [ 0 ]; // After the parent node is selected, the child node can only choose     
43      } 
 44  }
 45  int main ()
 46  {
 47      // freopen ("input.txt", "r", stdin);
 48      // freopen (" output.txt "," w ", stdout); 
49      std :: ios :: sync_with_stdio ( false );
 50      while (~ scanf ( " % d " , & n))
 51      {
52         f(i,1,n)
53         {
54             scanf("%d",&value[i]);
55             G[i].clear();
56             f[i]=-1;
57         }
58         while(1)
59         {
60             int a,b;
61             scanf("%d%d",&a,&b);
62             if(a==0&&b==0)break;
63             G[b].push_back(a);
64             f[a]=b;
65         }
66         int t=1;
67         while(f[t]!=-1)
68         {
69             t=f[t];
70         }
71         dfs(t);
72         printf("%d\n",max(dp[t][0],dp[t][1]));
73     }
74 }