WalkOverATree | Topcoder Archive

Problem Statement

Given is a tree on n nodes. The nodes are numbered 0 through n-1. You are given the description of the tree as a int[] parent with n-1 elements. For each valid i, there is an edge between vertices (i+1) and parent[i].

A person is currently standing in node 0. In a single step, the person can move from its current node to any adjacent node. You are given an int L. The person is allowed to make at most L steps.

Return the maximum number of nodes the person can visit during the walk. Node 0 (where the walk starts) and the node where the walk ends count as visited. Each visited node is only counted once, even if it is visited multiple times.

Definition

Class:: WalkOverATree
Method:: maxNodesVisited
Parameters:: int[], int
Returns:: int
Method signature:: int maxNodesVisited(int[] parent, int L)
(be sure your method is public)

Constraints

parent will contain between 0 and 49 elements, inclusive.
For each i, parent[i] will be between 0 and i, inclusive.
L will be between 1 and 100, inclusive.

Examples

```
{0, 0}
```
```
2
```
```
Returns: 2
```
The tree consists of edges 1-0 and 2-0. Our person will start in node 0 and can make at most L=2 steps. In two steps, the best we can do is visit one of the nodes 1 and 2.
```
{0, 0}
```
```
3
```
```
Returns: 3
```
This is the same tree, only now we have L=3. In three steps the person can visit all three nodes: for example, by going from node 0 to node 1, back to node 0, and finally to node 2. Note that even though the person visited node 0 twice, we only count it once.
```
{0, 1, 2, 3}
```
```
2
```
```
Returns: 3
```
```
{0,0,0,0,2,4,2,3,1}
```
```
1
```
```
Returns: 2
```

{0,0,1,2,3,2,3,1,3,0,1,8,6,8,0,5,15,0,9}

Returns: 5

{0,0,0,1,1,3,5,1,4,5,2,2,10,5,10,10,11,13,8,3,18,15,20,20,23,8,11,26,4}

Returns: 17

```
{0, 0, 2, 0}
```
```
100
```
```
Returns: 5
```
As the tree is very small and L large, the person can easily visit all nodes.
```
{0, 0, 2}
```
```
4
```
```
Returns: 4
```

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