POJ2342 Anniversary party

 1 #include<iostream>
 2 #include<algorithm>
 3 #include<cstdio>
 4 #include<cstring>
 5 #include<cmath>
 6 #include<cstdlib>
 7 #include<vector>
 8 using namespace std;
 9 typedef long long ll;
10 typedef long double ld;
11 typedef pair<int,int> pr;
12 #define rep(i,a,n) for(int i=a;i<=n;i++)
13 #define per(i,n,a) for(int i=n;i>=a;i--)
14 #define Rep(i,u) for(int i=head[u];i;i=Next[i])
15 #define clr(a) memset(a,0,sizeof(a))
16 #define pb push_back
17 #define mp make_pair
18 #define fi first
19 #define sc second
20 #define pq priority_queue
21 #define pqb priority_queue <int, vector<int>, less<int> >
22 #define pqs priority_queue <int, vector<int>, greater<int> >
23 #define vec vector
24 ld eps=1e-9;
25 ll pp=1000000007;
26 ll mo(ll a,ll pp){if(a>=0 && a<pp)return a;a%=pp;if(a<0)a+=pp;return a;}
27 ll powmod(ll a,ll b,ll pp){ll ans=1;for(;b;b>>=1,a=mo(a*a,pp))if(b&1)ans=mo(ans*a,pp);return ans;}
28 void fre() { freopen("c://test//input.in", "r", stdin); freopen("c://test//output.out", "w", stdout); }
29 //void add(int x,int y,int z){ v[++e]=y; next[e]=head[x]; head[x]=e; cost[e]=z; }
30 int dx[5]={0,-1,1,0,0},dy[5]={0,0,0,-1,1};
31 ll read(){ ll ans=0; char last=‘ ‘,ch=getchar();
32 while(ch<‘0‘ || ch>‘9‘)last=ch,ch=getchar();
33 while(ch>=‘0‘ && ch<=‘9‘)ans=ans*10+ch-‘0‘,ch=getchar();
34 if(last==‘-‘)ans=-ans; return ans;
35 }
36 const int N=10000;
37 int v[N],Next[N],head[N],dp[N][2],a[N],in[N],e;
38 void add(int x,int y){ v[++e]=y; Next[e]=head[x]; head[x]=e; }
39 void dfs(int x,int f){
40     for (int i=head[x];i;i=Next[i])
41     if (v[i]){
42         dfs(v[i],x);
43         dp[x][1]+=dp[v[i]][0];
44         dp[x][0]+=max(dp[v[i]][0],dp[v[i]][1]);
45     }
46 }
47 int main(){
48     int n=read();
49     for (int i=1;i<=n;i++) a[i]=read(),dp[i][1]=a[i];
50     int a_,b_,root;
51     while (~scanf("%d%d",&a_,&b_)){
52         if (a_==0 && b_==0) break;
53         add(b_,a_); in[a_]++;
54     }
55     for (int i=1;i<=n;i++)
56         if (!in[i]) root=i;
57     dfs(root,-1);
58     printf("%d",max(dp[root][1],dp[root][0]));
59     return 0;
60 }