The `Trail`

problem from the 2010 AP Computer Science Exam is typical of free response problems that test arrays. The problem requires you to find the minimum and maximum in an part of an array and access 2 elements of an array for each loop run.

`Trail`

is #3 from the 2010 AP Computer Science Free Response.

https://secure-media.collegeboard.org/apc/ap10_frq_computer_science_a.pdf

## Part (a) `isLevelTrailSegment`

method

```
public boolean isLevelTrailSegment(int start, int end)
{
int minElevation = markers[start];
int maxElevation = markers[start];
for (int i = start + 1; i <= end; i++)
{
if (markers[i] < minElevation)
minElevation = markers[i];
if (markers[i] > maxElevation)
maxElevation = markers[i];
}
return maxElevation - minElevation <= 10;
}
```

This is a find the min/max (both in this case) problem with the constraint that only the values at indexes from `start`

up to and including `end`

are considered. The algorithm is the same as any other find the max/min problem.

## Part (b) `isDifficult`

method

```
public boolean isDifficult()
{
int significantChanges = 0;
for (int i = 1; i < markers.length; i++)
if (Math.abs(markers[i - 1] - markers[i]) >= 30)
significantChanges++;
return significantChanges >= 3;
}
```

## 2010 AP CS Exam Free Response Solutions

## Help & comments

Get help from AP CS Tutor Brandon Horn