probs.txt

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                           GOLD PROBLEMS
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                  Six problems numbered 1 through 6
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Problem 1: Apple Catching [Hal Burch, 2004]

It is a little known fact that cows love apples.  Farmer John has
two apple trees (which are conveniently numbered 1 and 2) in his
field, each full of apples.  Bessie cannot reach the apples when
they are on the tree, so she must wait for them to fall.  However,
she must catch them in the air since the apples bruise when they
hit the ground (and no one wants to eat bruised apples).  Bessie
is a quick eater, so an apple she does catch is eaten in just a few
seconds.

Each minute, one of the two apple trees drops an apple. Bessie,
having much practice, can catch an apple if she is standing under
a tree from which one falls. While Bessie can walk between the two
trees quickly (in much less than a minute), she can stand under
only one tree at any time. Moreover, cows do not get a lot of
exercise, so she is not willing to walk back and forth between the
trees endlessly (and thus misses some apples).

Apples fall (one each minute) for T (1 <= T <= 1,000) minutes.
Bessie is willing to walk back and forth at most W (1 <= W <= 30)
times. Given which tree will drop an apple each minute, determine
the maximum number of apples which Bessie can catch.  Bessie starts
at tree 1.

POINTS: 500

PROBLEM NAME: bcatch

INPUT FORMAT:

* Line 1: Two space separated integers: T and W

* Lines 2..T+1: 1 or 2: the tree that will drop an apple each minute.

SAMPLE INPUT (file bcatch.in):

7 2
2
1
1
2
2
1
1

INPUT DETAILS:

Seven apples fall - one from tree 2, then two in a row from tree 1, then
two in a row from tree 2, then two in a row from tree 1. Bessie is
willing to walk from one tree to the other twice.

OUTPUT FORMAT:

* Line 1: The maximum number of apples Bessie can catch without
        walking more than W times.

SAMPLE OUTPUT (file bcatch.out):

6

OUTPUT DETAILS:

Bessie can catch six apples by staying under tree 1 until the first two
have dropped, then moving to tree 2 for the next two, then returning back
to tree 1 for the final two.

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Problem 2: Lake Counting [Hal Burch and Rob Kolstad, 2004]

Due to recent rains, water has pooled in various places in Farmer
John's field, which is represented by a rectangle of N x M (1 <= N
<= 100; 1 <= M <= 100) squares. Each square contains either water
('W') or dry land ('.').  Farmer John would like to figure out how
many ponds have formed in his field.  A pond is a connected set of
squares with water in them, where a square is considered adjacent
to all eight of its neighbors.

Given a diagram of Farmer John's field, determine how many ponds he has.

POINTS: 100

PROBLEM NAME: lkcount

INPUT FORMAT:

* Line 1: Two space-separated integers: N and M

* Lines 2..N+1: M characters per line representing one row of Farmer
        John's field.  Each character is either 'W' or '.'.  The
        characters do not have spaces between them.

SAMPLE INPUT (file lkcount.in):

10 12
W........WW.
.WWW.....WWW
....WW...WW.
.........WW.
.........W..
..W......W..
.W.W.....WW.
W.W.W.....W.
.W.W......W.
..W.......W.

OUTPUT FORMAT:

* Line 1: The number of ponds in Farmer John's field.

SAMPLE OUTPUT (file lkcount.out):

3

OUTPUT DETAILS:

There are three ponds: one in the upper left, one in the lower left,
and one along the right side.

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Problem 3: Til the Cows Come Home [Hal Burch, 2004]

Bessie is out in the field and wants to get back to the barn to get
as much sleep as possible before Farmer John wakes her for the
morning milking. Bessie needs her beauty sleep, so she wants to get
back as quickly as possible.

Farmer John's field has N (2 <= N <= 1000) landmarks in it, uniquely
numbered 1..N. Landmark 1 is the barn; the apple tree grove in which
Bessie stands all day is landmark N.  Cows travel in the field using
T (1 <= T <= 2000) bidirectional cow-trails of various lengths
between the landmarks. Bessie is not confident of her navigation
ability, so she always stays on a trail from its start to its end
once she starts it.

Given the trails between the landmarks, determine the minimum
distance Bessie must walk to get back to the barn.  It is guaranteed
that some such route exists.

POINTS: 100

PROBLEM NAME: cowhome

INPUT FORMAT:

* Line 1: Two integers: T and N

* Lines 2..T+1: Each line describes a trail as three space-separated
        integers.  The first two integers are the landmarks between
        which the trail travels. The third integer is the length of
        the trail, range 1..100.

SAMPLE INPUT (file cowhome.in):

5 5
1 2 20
2 3 30
3 4 20
4 5 20
1 5 100

INPUT DETAILS:

There are five landmarks.

OUTPUT FORMAT:

* Line 1: A single integer, the minimum distance that Bessie must
        travel to get from landmark N to landmark 1.

SAMPLE OUTPUT (file cowhome.out):

90

OUTPUT DETAILS:

Bessie can get home by following trails 4, 3, 2, and 1.

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Problem 4: Who's in the Middle [Kolstad, 2004]

FJ is surveying his herd to find the most average cow.  He wants
to know how much milk this 'median' cow gives: half of the cows
give as much or more than the median; half give as much or less.

Given an odd number of cows N (1 <= N < 10,000) and their milk output
(1..1,000,000), find the median amount of milk given such that at least
half the cows give the same amount of milk or more and at least half give
the same or less.

POINTS: 50

PROBLEM NAME: middle

INPUT FORMAT:

* Line 1: A single integer N

* Lines 2..N+1: Each line contains a single integer that is the milk
        output of one cow.

SAMPLE INPUT (file middle.in):

5
2
4
1
3
5

INPUT DETAILS:

Five cows with milk outputs of 1..5

OUTPUT FORMAT:

* Line 1: A single integer that is the median milk output.

SAMPLE OUTPUT (file middle.out):

3

OUTPUT DETAILS:

1 and 2 are below 3; 4 and 5 are above 3.

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Problem 5: Bull Math [kolstad, 2004]

Bulls are so much better at math than the cows. They can multiply
huge integers together and get perfectly precise answers ... or so
they say. Farmer John wonders if their answers are correct. Help
him check the bulls' answers. Read in two positive integers (no
more than 40 digits each) and compute their product.  Output it as
a normal number (with no extra leading zeros).

FJ asks that you do this yourself; don't use a special library
function for the multiplication.

POINTS: 50

PROBLEM NAME: bullmath

INPUT FORMAT:

* Lines 1..2: Each line contains a single decimal number.

SAMPLE INPUT (file bullmath.in):

11111111111111
1111111111

OUTPUT FORMAT:

* Line 1: The exact product of the two input lines

SAMPLE OUTPUT (file bullmath.out):

12345679011110987654321

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Problem 6: Bank Interest [Kolstad, 2004]

Farmer John made a profit last year! He would like to invest it
well but wonders how much money he will make. He knows the interest
rate R (an integer between 0 and 20) that is compounded annually
at his bank.  He has an integer amount of money M in the range
100..1,000,000.  He knows how many years Y (range: 0..400) he intends
to invest the money in the bank. Help him learn how much money he
will have in the future by compounding the interest for each year
he saves.  Print an integer answer without rounding. Answers for the test
data are guaranteed to fit into a signed 32 bit integer.

POINTS: 50

PROBLEM NAME: bankint

INPUT FORMAT:

* Line 1: Three space-separated integers: R, M, and Y

SAMPLE INPUT (file bankint.in):

5 5000 4

INPUT DETAILS:

5% annual interest, 5000 money, 4 years

OUTPUT FORMAT:

* Line 1: A single integer that is the number of dollars FJ will have
        after Y years.

SAMPLE OUTPUT (file bankint.out):

6077

OUTPUT DETAILS:

Year 1: 1.05 * 5000 = 5250
Year 2: 1.05 * 5250 = 5512.5
Year 3: 1.05 * 5512.50 = 5788.125
Year 4: 1.05 * 5788.125 = 6077.53125
The integer part of 6077.53125 is 6077.

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