Anniversary party
There is going to be a party to celebrate the 80-th Anniversary of the Ural State University. The University has a hierarchical structure of employees. It means that the supervisor relation forms a tree rooted at the rector V. E. Tretyakov. In order to make the party funny for every one, the rector does not want both an employee and his or her immediate supervisor to be present. The personnel office has evaluated conviviality of each employee, so everyone has some number (rating) attached to him or her. Your task is to make a list of guests with the maximal possible sum of guests' conviviality ratings.
Input
Employees are numbered from 1 to N. A first line of input contains a number N. 1 <= N <= 6 000. Each of the subsequent N lines contains the conviviality rating of the corresponding employee. Conviviality rating is an integer number in a range from -128 to 127. After that go N – 1 lines that describe a supervisor relation tree. Each line of the tree specification has the form:
L K
It means that the K-th employee is an immediate supervisor of the L-th employee. Input is ended with the line
0 0
Output
Output should contain the maximal sum of guests' ratings.
Sample Input
7
1
1
1
1
1
1
1
1 3
2 3
6 4
7 4
4 5
3 5
0 0
Sample Output
5
Source
Ural State University Internal Contest October'2000 Students Session
题目类型：树形DP
算法分析：使用dp[i][0]和dp[i][1]分别表示以第i个节点为子树且i来、不来时的最大喜欢直，然后使用树的后序遍历从叶子节点开始将每个节点的最大喜欢值求出来，注意本题中没有告诉root位置，所以需要自己在输入中找
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#include <set> #include <bitset> #include <list> #include <map> #include <stack> #include <queue> #include <deque> #include <string> #include <vector> #include <ios> #include <iostream> #include <fstream> #include <sstream> #include <iomanip> #include <algorithm> #include <utility> #include <complex> #include <numeric> #include <functional> #include <cmath> #include <ctime> #include <climits> #include <cstdarg> #include <cstdio> #include <cstdlib> #include <cstring> #include <cctype> #include <cassert> using namespace std; const int INF = 0x7FFFFFFF; const int MOD = 7; const double EPS = 1e-10; const double PI = 2 * acos (0.0); const int maxn = 6000 + 66; int dp[maxn][2], parent[maxn], vis[maxn]; int n; void dfs (int root) { vis[root] = 1; for (int i = 1; i <= n; i++) if (!vis[i] && parent[i] == root) { dfs (i); dp[root][1] += dp[i][0]; dp[root][0] += max (dp[i][0], dp[i][1]); } } int main() { // ifstream cin ("aaa.txt"); while (cin >> n) { memset (dp, 0, sizeof (dp)); for (int i = 1; i <= n; i++) cin >> dp[i][1]; memset (parent, 0, sizeof (parent)); memset (vis, 0, sizeof (vis)); int a, b, root = 0; while (cin >> a >> b) { if (a == 0 && b == 0) break; parent[a] = b; root = b; } dfs (root); cout << max (dp[root][0], dp[root][1]) << endl; } return 0; } |
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