Wust-1299-node selection (tree DP)

Problem Description has a tree with n nodes. each node in the tree has a positive integer weight. If a vertex is selected, the vertex adjacent to the tree cannot be selected. What is the weight and maximum value of the selected vertex?

The first line of Input contains an integer n. The next row contains n positive integers. The I positive integers represent the weights of vertex I. Next there are a total of N-1 rows, each line describes an edge on the tree.

Output outputs an integer representing the weights and maximum values of the selected vertex.

Sample Input

51 2 3 4 51 21 32 42 5

Sample Output

12

HINT

Example
Select 3, 4, and 5. The weight is 3 + 4 + 5 = 12.

Data scale and conventions
For 20% of data, n <= 20.
For 50% of data, n <= 1000.
For 100% of data, n <= 100000.
The weights are all positive integers not greater than 1000.
Train of Thought: For each vertex I, either select val [I] + gson [I], where gson [I] indicates the sum of the dp values of all grandson nodes; or do not select: son [I], where son [I] indicates the sum of the dp values of all son nodes. There is no root tree in the question. You only need to select a node as the root node (select 1 here) to determine the parent-child relationship. Then we use an array to simulate the stack, and finally start pushing forward from the last element of the array (this is equivalent to pushing up from the bottom layer of the tree ), and the son value of the new parent node and the gson value of the grandfather node.

# Include
 
  
Using namespace std; int val [100001], dp [100001], son [100001], gson [100001], first [100001], next [200002], to [200002], que [100001], far [100001]; bool vis [100001]; int main () {int n, I, u, v, ans; while (~ Scanf ("% d", & n) {for (I = 1; I <= n; I ++) first [I] =-1, vis [I] = son [I] = gson [I] = dp [I] = 0; for (I = 1; I <= n; I ++) scanf ("% d", & val [I]); for (I = 0; I
  
   
= 0; I --) // start from the bottom layer of the tree and push up {dp [que [I] = val [que [I] + gson [que [I]> son [que [i]? Val [que [I] + gson [que [I]: son [que [I]; ans = ans> dp [que [I]? Ans: dp [que [I]; if (far [que [I]! =-1) {son [far [que [I] + = dp [que [I]; // update the son value of the parent node if (far [far [que [I]! =-1) gson [far [far [que [I] + = dp [que [I]; // update the gson value of the grandfather node} printf ("% d \ n", ans );}}