1273. Delete Tree Nodes

A tree rooted at node 0 is given as follows:

• The number of nodes is nodes ;
• The value of the i -th node is value[i] ;
• The parent of the i -th node is parent[i] .

Remove every subtree whose sum of values of nodes is zero.

After doing so, return the number of nodes remaining in the tree.

Example 1:

Input:

 nodes = 7, parent = [-1,0,0,1,2,2,2], value = [1,-2,4,0,-2,-1,-1]
Output:

 2

Constraints:

• 1 <= nodes <= 10^4
• -10^5 <= value[i] <= 10^5
• parent.length == nodes
• parent[0] == -1  which indicates that 0 is the root.