BNUOJ 2461 Anniversary party

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <climits>
 7 #include <vector>
 8 #include <queue>
 9 #include <cstdlib>
10 #include <string>
11 #include <set>
12 #include <stack>
13 #define LL long long
14 #define pii pair<int,int>
15 #define INF 0x3f3f3f3f
16 using namespace std;
17 const int maxn = 6010;
18 int dp[maxn][2],w[maxn],n,in[maxn];
19 vector<int>g[maxn];
20 void dfs(int u,int fa){
21     dp[u][1] = w[u];
22     for(int i = 0; i < g[u].size(); i++){
23         if(g[u][i] == fa) continue;
24         dfs(g[u][i],u);
25         dp[u][1] += dp[g[u][i]][0];//u来，g[u][i]不来
26         dp[u][0] += max(dp[g[u][i]][1],dp[g[u][i]][0]);
27         //u不来，g[u][i]来或者不来
28     }
29 }
30 int main() {
31     int i,j,u,v,tmp;
32     while(~scanf("%d",&n)){
33         for(i = 1; i <= n; i++){
34             scanf("%d",w+i);
35             g[i].clear();
36             in[i] = 0;
37             dp[i][0] = dp[i][1] = 0;
38         }
39         for(i = 1; i; i++){
40             scanf("%d %d",&u,&v);
41             if(u+v == 0) break;
42             g[u].push_back(v);
43             g[v].push_back(u);
44             in[v]++;
45         }
46         for(i = 1; i <= n; i++){
47             if(!in[i]){dfs(i,-1);break;}
48         }
49         printf("%d\n",max(dp[i][0],dp[i][1]));
50     }
51     return 0;
52 }