Usaco Chn07

Special Chinese USACO Contest (1 Division) 2007

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GOLD PROBLEMS
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Three problems numbered 1 through 3
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Problem 1: Summing Sums [Neal Wu, 2007]

The N (1 <= N <= 50,000) cows, conveniently numbered 1..N, are
trying to learn some encryption algorithms. After studying a few
examples, they have decided to make one of their own! However, they
are not very experienced at this, so their algorithm is very simple:

Each cow i is given a starting number C_i (0 <= C_i < 90,000,000),
and then all the cows perform the following process in parallel:

* First, each cow finds the sum of the numbers of the other N-1
cows.

* After all cows are finished, each cow replaces her number
with the sum she computed. To avoid very large numbers, the
cows will keep track of their numbers modulo 98,765,431.

They told Canmuu the moose about it in November; he was quite
impressed.

Then one foggy Christmas Eve, Canmuu came to say:

"Your algorithm is too easy to break! You should repeat it T
(1 <= T <= 1,414,213,562) times instead."

Obviously, the cows were very frustrated with having to perform so
many repetitions of the same boring algorithm, so after many hours
of arguing, Canmuu and the cows reached a compromise: You are to
calculate the numbers after the encryption is performed!

*Some extra feedback will be provided for the first 10 submissions to
this
problem.

PROBLEM NAME: sumsums

INPUT FORMAT:

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

* Lines 2..N+1: Line i+1 contains a single integer: C_i

SAMPLE INPUT (file sumsums.in):

3 4
1
0
4

INPUT DETAILS:

Three cows, with starting numbers 1, 0, and 4; four repetitions of the
encryption algorithm.

OUTPUT FORMAT:

* Lines 1..N: Line i contains a single integer representing the number
of cow i (modulo 98,765,431) at the end of the encryption.

SAMPLE OUTPUT (file sumsums.out):

26
25
29

OUTPUT DETAILS:

The following is a table of the cows' numbers for each turn:

Cows' numbers
Turn    Cow1  Cow2  Cow3
0        1     0     4
1        4     5     1
2        6     5     9
3       14    15    11
4       26    25    29

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Problem 2: The Bovine Accordion and Banjo Orchestra [Lei Huang, 2007]

The 2*N (3 <= N <= 1,000) cows have assembled the Bovine Accordion
and Banjo Orchestra!  They possess various levels of skill on their
respective instruments: accordionist i has an associated talent
level A_i (0 <= A_i <= 1,000); banjoist j has an associated talent
level B_j (0 <= B_j <= 1,000).

The combined `awesomeness' of a pairing between cows with talents
A_i and B_j is directly proportional to the talents of each cow in
the pair so a concert with those two cows will earn FJ precisely
A_i * B_j dollars in "charitable donations".  FJ wishes to maximize
the sum of all revenue obtained by his cows by pairing them up in
the most profitable way.

Unfortunately, FJ's accordionists are a bit stuck up and stubborn.
If accordionist i is paired with banjoist j, then accordionists
i+1..N refuse to be paired with banjoists 1..j-1. This creates
restrictions on which pairs FJ can form. FJ thus realizes that in
order to maximize his profits, he may have to leave some cows
unpaired.

To make matters worse, when one or more of the musicians is skipped,
they will be greatly upset at their wasted talent and will engage
in massive binge drinking to wash away their sorrows.

After all pairings are made, a list is constructed of the groups
of each of the consecutive skipped musicians (of either instrument).
Every group of one or more consecutive skipped cows will gather
together to consume kegs of ice cold orange soda in an amount
proportional to the square of the sum of their wasted talent.

Specifically, FJ has calculated that if the x-th to y-th accordionists
are skipped, they will consume precisely (A_x + A_x+1 + A_x+2 + ...
+ A_y)^2 dollars worth of orange soda in the process of drinking
themselves into oblivion. An identical relationship holds for the
banjoists. FJ realizes that he'll end up getting stuck with the
bill for his cows' drinking, and thus takes this into account when
choosing which pairings to make.

Find the maximum amount of total profit that FJ can earn after the
contributions are collected and the orange soda is paid for.

Memory Limit: 64MB

PROBLEM NAME: baabo

INPUT FORMAT:

* Line 1: A single integer: N

* Lines 2..N+1: Line i+1 contains the single integer: A_i

* Lines N+2..2*N+1: Line i+N+1 contains the single integer: B_i

SAMPLE INPUT (file baabo.in):

3
1
1
5
5
1
1

INPUT DETAILS:

There are 6 cows: 3 accordionists and 3 banjoists. The accordionists
have
talent levels (1, 1, 5), and the banjoists have talent levels (5, 1, 1).

OUTPUT FORMAT:

* Line 1: A single integer that represents the maximum amount of cash
that FJ can earn.

SAMPLE OUTPUT (file baabo.out):

17

OUTPUT DETAILS:

FJ pairs accordionist 3 with banjoist 1 to get earn A_3 * B_1 = 5 * 5 =
25
in profit.  He loses a total of (1 + 1)^2 + (1 + 1)^2 = 8 dollars due to
the cost of soda for his remaining cows. Thus his final (net) profit is
25
- 8 = 17.

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Problem 3: Treasure [Yang Yi, 2007]

Canmuu and his friends have recently acquired a large cache of
plutonium and have agreed to bury their newfound treasure at some
road intersection deep in the Canadian wilderness. Any sort of treasure
burial calls for a treasure map so they've decided to create one
of their own.

The road network consists of N (4 <= N <= 100,000) intersections
(conveniently numbered 1..N) with N roads connecting them. As busy
intersections confuse everybody, every intersection has at least
one road that leads to it, and no intersection has more than four
roads connected to it. Excellent maintenance has ensured that a
moose can always run either way between any pair of intersections.
Furthermore, Canmuu has decided the plutonium should not be buried
at any of the 4-way intersections since busy traffic decreases the
secrecy of the buried treasure.

The treasure map will contain all the roads and all the intersections.
But, to conceal the treasure's location, only one road intersection
on the treasure map is to be labeled: the intersection at which the
treasure is buried (which has a big red 'X', of course).

Ever the alert moose, Canmuu drew some trial maps to see what they
would look like depending on where the treasure was buried. Canmuu
noticed that the moose might draw similar maps even if they bury
their treasure in two different locations. Their curiosity piqued,
the herd began trying to figure out how many distinct maps they
could end up making.

Maps are indistinct if it is possible to assign a mapping such that:

* the X-labeled intersections on both maps correspond,

* a correspondence can be created for the other intersections,
such that

* when the well-chosen intersection correspondence is determined,
the roads that connect the intersections also correspond.

By way of example, consider the maps below where N = 4; the treasure
might be buried at any of four intersections:

+             +             X           +
/|            /|            /|          /|
X---+ |       +---X |       +---+ |     +---+ |
\|            \|            \|          \|
+             +             +           X

The final two maps, however, are not distinct since one can create
a correspondence for the vertices (consider the map upside down)
and then the roads correspond exactly. Thus, only three maps are
distinct.

How many distinct maps are possible for a given set of roads?

TIME LIMIT: 1 second; might be increased for big test cases

MEMORY LIMIT: 64MB

*Some extra feedback will be provided for the first 10 submissions to
this
problem.

PROBLEM NAME: treasure

INPUT FORMAT:

* Line 1: A single integer: N

* Lines 2..N + 1: Two space-separated integers: A and B (1 <= A <= N;
1 <= B <= N), indicating that there is a road connecting
intersections A and B

SAMPLE INPUT (file treasure.in):

4
1 2
2 3
3 1
1 4

INPUT DETAILS:

Here is a drawing of the roads and the intersections.

4---1---2
\ /
3

OUTPUT FORMAT:

* Line 1: A single integer that is the number of distinct treasure
maps

SAMPLE OUTPUT (file treasure.out):

3

OUTPUT DETAILS:

The treasure can be buried at any intersection. However, burying it at
intersections 2 and 3 yields maps that are identical to each other. So
the
total number of distinct treasure maps is 3.

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page revision: 3, last edited: 08 Jul 2011 02:44