Ural 1039 Anniversary Party

题目链接：http://acm.timus.ru/problem.aspx?space=1&num=1039

Dynamic Programming. 建立树形结构，每个employee有两个选择，去或者不去。supervisor的选择影响着sub-tree的选择。代码如下：

 #include <iostream>
 #include <math.h>
 #include <stdio.h>
 #include <cstdio>
 #include <algorithm>
 #include <string.h>
 #include <string>
 #include <sstream>
 #include <cstring>
 #include <queue>
 #include <vector>
 #include <functional>
 #include <cmath>
 #include <set>
 #define SCF(a) scanf("%d", &a)
 #define IN(a) cin>>a
 #define FOR(i, a, b) for(int i=a;i<b;i++)
 #define Infinity 9999999
 typedef long long Int;
 using namespace std;

 struct tree {
     int parent;
     vector<int> children;
     int size = ;
 };
 int N;
 tree * trees[];
 int dp[][]; //i -> employee id, j -> attend 1 or not 0
 int conviviality[];

 int calcuTree(int parent, int choice) //choice 1: attend or not, choice 0: cannot atted
 {
     if (dp[parent][choice] != Infinity)
         return dp[parent][choice];

     int maxCon = ;
     int maxConDGo = ;
     int maxConGo = conviviality[parent];
     //this employee don't go, its child has 2 choices
     for (int i = ; i < trees[parent]->size; i++)
     {
         int child = trees[parent]->children[i];
         if (dp[child][] == Infinity)
             dp[child][] = calcuTree(child, );
         if (dp[child][] == Infinity)
             dp[child][] = calcuTree(child, );
         maxConDGo += max(dp[child][], dp[child][]);
     }

     //this employee go, its child has only one choice.
     for (int i = ; i < trees[parent]->size; i++)
     {
         int child = trees[parent]->children[i];
         if (dp[child][] == Infinity)
             dp[child][] = calcuTree(child, );
         maxConGo += dp[child][];
     }

     if (choice == )
         maxCon = max(maxConGo, maxConDGo);
     else
         maxCon = maxConDGo;

     return maxCon;
 }

 int main()
 {
     while (SCF(N) != EOF)
     {
         FOR(i, , N + )
             SCF(conviviality[i]);
         int L, K;
         int index = ;
         FOR(i, , N + )
         {
             trees[i] = new tree;
             trees[i]->parent = i;
         }

         bool *root = new bool[N + ];
         FOR(i, , N + )
             root[i] = true;

         while (scanf("%d %d", &L, &K))
         {
             if (L ==  && K == )
                 break;
             trees[K]->children.push_back(L);
             trees[K]->size += ;
             root[L] = false;
         }

         FOR(i, , N + )
         {
             dp[i][] = dp[i][] = Infinity;
         }

         int president = ;
         FOR(i, , N + )
         {
             if (root[i])
             {
                 president = i;
                 break;
             }
         }

         FOR(i, , N + )
         {
             dp[i][] = calcuTree(i, );
             dp[i][] = calcuTree(i, );
         }

         int maxAns = max(dp[president][], dp[president][]);
         printf("%d\n", maxAns);
     }
     return ;
 }