TheTree | Topcoder Archive

Problem Statement

Manao is working in the Tree Research Center. It may come as a surprise that the trees they research are not the ones you can see in a park. Instead, they are researching special graphs. (See Notes for definitions of terms related to these trees.)

Manao's daily job is reconstructing trees, given some partial information about them. Today Manao faced a difficult task. He needed to find the maximum possible diameter of a tree, given the following information:

Some vertex in the tree is called V.
The distance between V and the farthest vertex from V is D.
For each x between 1 and D, inclusive, Manao knows the number of vertices such that their distance from V is x.

You are given a int[] cnt containing D strictly positive integers. For each i, the i-th element of cnt is equal to the number of vertices which have distance i+1 from V. Please help Manao with his task. Return the maximum possible diameter of a tree that matches the given information.

Definition

Class:: TheTree
Method:: maximumDiameter
Parameters:: int[]
Returns:: int
Method signature:: int maximumDiameter(int[] cnt)
(be sure your method is public)

Notes

A tree is a connected graph with no cycles. Note that each tree with N vertices has precisely N-1 edges.
The distance between two vertices of a tree is the smallest number of edges one has to traverse in order to get from one of the vertices to the other one.
The diameter of a tree is the maximum of all pairwise distances. In other words, the diameter is the distance between the two vertices that are the farthest away from each other.

Constraints

cnt will contain between 1 and 50 elements, inclusive.
Each element of cnt will be between 1 and 1000, inclusive.

Examples

```
{3}
```
```
Returns: 2
```
The only tree that matches the given information is shown below. The vertex V is red.
```
{2, 2}
```
```
Returns: 4
```
There are two trees which correspond to the given partial information: The tree on the left has diameter 3 and the tree on the right has diameter 4.
```
{4, 1, 2, 4}
```
```
Returns: 5
```
This is one example of a tree that corresponds to the given constraints and has the largest possible diameter.

{4, 2, 1, 3, 2, 5, 7, 2, 4, 5, 2, 3, 1, 13, 6}

Returns: 21

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