Usaco Nov09 Bronze

Part of USACO Nov09

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BRONZE PROBLEMS
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Three problems numbered 11 through 13
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Problem 11: Claustrophobic Cows [Rob Kolstad, 2009]

Farmer John has acquired a set of N (2 <= N <= 2,000) touchy cows
who are conveniently numbered 1..N. They really hate being too close
to other cows. A lot.

FJ has recorded the integer X_i,Y_i coordinates of every cow i (1
<= X_i <= 100,000; 1 <= Y_i <= 100,000).

Among all those cows, exactly two of them are closest together. FJ
would like to spread them out a bit. Determine which two are closest
together and print their cow id numbers (i) in numerical order.

By way of example, consider this field of cows (presented on a
typewriter grid that has slightly different proportions than you
might expect):

10 | . . . . . . . 3 . . . . .
9 | . 1 . . 2 . . . . . . . .
8 | . . . . . . . . . . . . .
7 | . . . . . . . . . . 4 . .
6 | . . . . . . 9 . . . . . .
5 | . 8 . . . . . . . . . . .
4 | . . . . . 7 . . . . . . .
3 | . . . . . . . . . 5 . . .
2 | . . . . . . . . . . . . .
1 | . . . . 6 . . . . . . . .
0 ---------------------------
1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3

Quick visual inspection shows that cows 7 and 9 are closest together
(the distance separating them is sqrt(1*1+2*2) = sqrt(5), so the
output would be '7 9' on a single line (without quotes, of course).

PROBLEM NAME: claust

INPUT FORMAT:

* Line 1: A single integer: N

* Lines 2..N+1: Line i contains the coordinates of cow i expressed as
two space-separated integers: X_i and Y_i

SAMPLE INPUT (file claust.in):

9
2 9
5 9
8 10
11 7
10 3
5 1
6 4
2 5
7 6

INPUT DETAILS:

As in the example.

OUTPUT FORMAT:

* Line 1: The two numerical IDs of the closest pair of cows (sorted)

SAMPLE OUTPUT (file claust.out):

7 9

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Problem 12: The Chivalrous Cow [Rob Kolstad, 2009]

Farmer John traded one of his cows for a cow that Farmer Don called
'The Knight'. This cow has the unique ability to jump around the
pasture in moves that looked like a knight on a chessboard (two
squares over, one up... or maybe two squares down and one over,
etc.). 'The Knight' can't jump on rocks or trees, but can really
make her way around the pasture, which is partitioned for our
purposes into an X by Y set of squares (1 <= X <= 150; 1 <= Y <=
150).

'The Knight' likes hay just like any other cow. Given a map of 'The
Knight's starting place, locations of the tree, shrub, rock, and
other obstacles, and the location of a bale of hay, determine how
many 'hops' the Knight must make in order to get to the hay. The
Knight cow will be marked by a 'K' on the map; obstacles by '*',
and the haybale by 'H'. Here's a typical map:

11 | . . . . . . . . . .
10 | . . . . * . . . . .
9 | . . . . . . . . . .
8 | . . . * . * . . . .
7 | . . . . . . . * . .
6 | . . * . . * . . . H
5 | * . . . . . . . . .
4 | . . . * . . . * . .
3 | . K . . . . . . . .
2 | . . . * . . . . . *
1 | . . * . . . . * . .
0 ----------------------
1
0 1 2 3 4 5 6 7 8 9 0

The knight could travel the path indicated by A, B, C, ... to get
to the hay bale in just 5 moves (other routes of length 5 might be
possible):

11 | . . . . . . . . . .
10 | . . . . * . . . . .
9 | . . . . . . . . . .
8 | . . . * . * . . . .
7 | . . . . . . . * . .
6 | . . * . . * . . . F<
5 | * . B . . . . . . .
4 | . . . * C . . * E .
3 | .>A . . . . D . . .
2 | . . . * . . . . . *
1 | . . * . . . . * . .
0 ----------------------
1
0 1 2 3 4 5 6 7 8 9 0

Hint: This problem is probably most easily solved with a simple
first-in/first-out 'queue' data structure implemented as a few
parallel arrays.

PROBLEM NAME: kcow

INPUT FORMAT:

* Line 1: Two space-separated integers: X and Y

* Lines 2..Y+1: Line Y-i+2 contains X characters with no spaces (i.e.,
the map is read in as shown in the text above): map row i

SAMPLE INPUT (file kcow.in):

10 11
..........
....*.....
..........
...*.*....
.......*..
..*..*...H
*.........
...*...*..
.K........
...*.....*
..*....*..

OUTPUT FORMAT:

* Line 1: A single integer that is the minimum number of hops to get
to the hay bale. It is always possible to get to the haybale.

SAMPLE OUTPUT (file kcow.out):

5

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Problem 13: Cow Pinball [Traditional, 2009]

The cows are playing that cool Japanese 'pinball' game called
Pachinko. You've probably seen it, you drop a ball in the top and
it hits nails on the way down, veering just a little left or right,
until the ball comes out the bottom.

This pachinko game is special: the ball always hits the top nail
of the R rows of nails (1 <= R <= 25) and then will hit either the
right or left nail underneath that.  From there, the ball can hit
the next nail that's just a bit lower and to the left or right of
the second nail, and so on. The ball never veers too far (i.e.,
more than 1/2 nail away) from the nail it just hit.

This game also has scoring that's unique: you get points X_ij (0
<= X_ij <= 3,000) for each little nail you hit on the way down. The
cows want to maximize their score on this machine. What is the best
score they can achieve?

Here's an example triangle and a good route:

7                        *7

3   8                    *3   8

8   1   0                *8   1   0

2   7   4   4             2  *7   4   4

4   5   2   6   5         4  *5   2   6   5

In the sample above, the route from 7 to 3 to 8 to 7 to 5 produces
the highest sum: 30. It's not possible to go from 7 to 8 to 8 --
the 8 on the third row is too far away.

PROBLEM NAME: pachinko

INPUT FORMAT:

* Line 1: A single integer: R

* Lines 2..R+1: Line i+1 contains i space-separated integers that
compose the scores of row R of the pachinko machine: X_i1,
X_i2, ...

SAMPLE INPUT (file pachinko.in):

5
7
3 8
8 1 0
2 7 4 4
4 5 2 6 5

OUTPUT FORMAT:

* Line 1: A single integer that is the maximum achievable score.

SAMPLE OUTPUT (file pachinko.out):

30

OUTPUT DETAILS:

No other achievable sum is higher.

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page revision: 0, last edited: 11 Dec 2009 02:35