SumPairs | Topcoder Archive

Problem Statement

Given a list of distinct integers, return how many different pairs of them sum up to result. A pair is any 2 numbers from the given values. 2 pairs are different if any of their elements are different.

Definition

Class:: SumPairs
Method:: howMany
Parameters:: int[], int
Returns:: int
Method signature:: int howMany(int[] values, int result)
(be sure your method is public)

Constraints

values will contain between 2 and 50 elements inclusive.
Each element of values will be between -1000 and 1000 inclusive
Each element of values will be distinct.
result will be between -50000 and 50000 inclusive.

Examples

```
{2,3}
```
```
5
```
```
Returns: 1
```
The only pair consists of 2 and 3. It does indeed sum to 5.
```
{2,3}
```
```
10
```
```
Returns: 0
```
Same as before, but the pair doesn't sum to 10.
```
{2,4,5,1}
```
```
6
```
```
Returns: 2
```
The only 2 pairs of numbers that sum to 6 are (2,4) and (5,1). Note, there are 4 other pairs that do not work.
```
{1,2,3,4,5,6,7,8,9,10}
```
```
11
```
```
Returns: 5
```

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