hdu 1520 Anniversary party

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

 1 #include <cstdio>

 2 #include <vector>

 3 #include <cstring>

 4 #include <algorithm>

 5 #define maxn 7000

 6 using namespace std;

 7 

 8 int dp[maxn][3];

 9 int a[maxn],pre[maxn];

10 int n,u,v;

11 vector<int>g[maxn];

12 

13 void dfs(int m)

14 {

15     dp[m][1]=a[m];

16     for(int i=0; i<(int)g[m].size(); i++)

17     {

18         int v2=g[m][i];

19         dfs(v2);

20         dp[m][0]+=(max(dp[v2][0],dp[v2][1]));

21         dp[m][1]+=dp[v2][0];

22     }

23 }

24 

25 int main()

26 {

27     while(scanf("%d",&n)!=EOF)

28     {

29         memset(a,0,sizeof(a));

30         memset(pre,-1,sizeof(pre));

31         memset(dp,0,sizeof(dp));

32         for(int i=1; i<=n; i++)

33         {

34             g[i].clear();

35         }

36         for(int i=1; i<=n; i++)

37         {

38             scanf("%d",&a[i]);

39         }

40         int c;

41         while(scanf("%d%d",&u,&v))

42         {

43             if(u==0&&v==0) break;

44             c=u;

45             g[v].push_back(u);

46             pre[u]=v;

47         }

48         while(pre[c]!=-1)

49         {

50             c=pre[c];

51         }

52         dfs(c);

53         int ans=max(dp[c][1],dp[c][0]);

54         printf("%d\n",ans);

55     }

56     return 0;

57 }

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