【树形DP】P1352 没有上司的舞会

 1 #include<iostream>
 2 #include<string>
 3 #include<queue>
 4 #include<stack>
 5 #include<vector>
 6 #include<map>
 7 #include<cstdio>
 8 #include<cstdlib>
 9 #include<algorithm>
10 #include<set>
11 #include<list>
12 #include<iomanip>
13 #include<cstring>
14 #include<cmath>
15 #include<limits>
16 using namespace std;
17 
18 #define au auto
19 #define debug(i) cout<<"<debug> "<<i<<"<\debug>"<<endl
20 #define mfor(i,a,b) for(register int i=(a);i<=(b);i++)
21 #define mrep(i,a,b) for(register int i=(a);i>=(b);i--)
22 #define LLL __int128
23 #define Re register
24 #define il inline
25 #define mem(a,b) memset(a,(b),sizeof(a))
26 typedef pair<int, int> intpair;
27 typedef long long int LL;
28 const int INF = 0x3f3f3f3f;
29 const long long int INFLL = 0x3f3f3f3f3f3f3f3f;
30 
31 int cnt;
32 const int maxn = 6010;
33 int n;
34 int r[maxn];
35 int f[maxn][2];
36 bool vis[maxn];
37 
38 struct Edge
39 {
40     int u, nxt;
41 }e[maxn];
42 
43 int head[maxn];
44 
45 void add(int a, int b)
46 {
47     e[++cnt].u = b;
48     e[cnt].nxt = head[a];
49     head[a] = cnt;
50 }
51 
52 void dp(int x)
53 {
54     f[x][0] = 0;
55     f[x][1] = r[x];
56     for (Re int i = head[x]; i != -1; i = e[i].nxt)
57     {
58         dp(e[i].u);
59         f[x][0] += max(f[e[i].u][0], f[e[i].u][1]);
60         f[x][1] += f[e[i].u][0];
61     }
62 }
63 
64 int main()
65 {
66     mem(head, -1);
67     cin >> n;
68     mfor(i, 1, n) cin >> r[i];
69     mfor(i, 1, n - 1)
70     {
71         int a, b;
72         cin >> a >> b;
73         add(b, a);
74         vis[a] = true;
75     }
76     int root;
77     mfor(i, 1, n)
78     {
79         if (!vis[i])
80         {
81             root = i;
82             break;
83         }
84     }
85     dp(root);
86     cout << max(f[root][0], f[root][1]);
87     return 0;
88 }

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