Usaco Nov09 Silver

Part of USACO Nov09

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SILVER PROBLEMS
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Three problems numbered 6 through 8
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Problem 6: A Coin Game [Osman Ay, 2009]
Farmer John's cows like to play coin games so FJ has invented with
a new two-player coin game called Xoinc for them.
Initially a stack of N (5 <= N <= 2,000) coins sits on the ground;
coin i from the top has integer value C_i (1 <= C_i <= 100,000).
The first player starts the game by taking the top one or two coins
(C_1 and maybe C_2) from the stack. If the first player takes just
the top coin, the second player may take the following one or two
coins in the next turn. If the first player takes two coins then
the second player may take the top one, two, three or four coins
from the stack. In each turn, the current player must take at least
one coin and at most two times the amount of coins last taken by
the opposing player. The game is over when there are no more coins
to take.
Afterwards, they can use the value of the coins they have taken
from the stack to buy treats from FJ, so naturally, their purpose
in the game is to maximize the total value of the coins they take.
Assuming the second player plays optimally to maximize his own
winnings, what is the highest total value that the first player can
have when the game is over?
MEMORY LIMIT: 20 MB
PROBLEM NAME: xoinc
INPUT FORMAT:
* Line 1: A single integer: N
* Lines 2..N+1: Line i+1 contains a single integer: C_i
SAMPLE INPUT (file xoinc.in):
5
1
3
1
7
2
INPUT DETAILS:
There are five coins with the values 1, 3, 1, 7, and 2.
OUTPUT FORMAT:
* Line 1: A single integer representing the maximum value that can be
made by the first player.
SAMPLE OUTPUT (file xoinc.out):
9
OUTPUT DETAILS:
The first player starts by taking a single coin (value 1). The
opponent takes one coin as well (value 3). The first player takes
two more coins (values 1 and 7 -- total 9). The second player gets
the leftover coin (value 2-- total 5).
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Problem 7: The Grand Farm-off [Haitao Mao, 2009]
Farmer John owns 3*N (1 <= N <= 500,000) cows surprisingly numbered
0..3*N-1, each of which has some associated integer weight W_i (1 <=
W_i <= d). He is entering the Grand Farm-off, a farming competition
where he shows off his cows to the greater agricultural community.
This competition allows him to enter a group of N cows. He has given
each of his cows a utility rating U_i (1 <= U_i <= h), which
represents the usefulness he thinks that a particular cow will have
in the competition, and he wants his selection of cows to have the
maximal sum of utility.
There might be multiple sets of N cows that attain the maximum
utility sum. FJ is afraid the competition may impose a total weight
limit on the cows in the competition, so a secondary priority is
to bring lighter weight competition cows.
Help FJ find a set of N cows with minimum possible total weight
among the sets of N cows that maximize the utility, and print the
remainder when this total weight is divided by M (10,000,000 <= M
<= 1,000,000,000).
Note: to make the input phase faster, FJ has derived polynomials
which will generate the weights and utility values for each cow.
For each cow 0 <= i < 3*N,
W_i = (a*i^5+b*i^2+c) mod d
and U_i = (e*i^5+f*i^3+g) mod h
with reasonable ranges for the coefficients (0 <= a <= 1,000,000,000;
0 <= b <= 1,000,000,000; 0 <= c <= 1,000,000,000; 0 <= e <=
1,000,000,000; 0 <= f <= 1,000,000,000; 0 <= g <= 1,000,000,000;
10,000,000 <= d <= 1,000,000,000; 10,000,000 <= h <= 1,000,000,000).
The formulae do sometimes generate duplicate numbers; your algorithm
should handle this properly.
PROBLEM NAME: farmoff
INPUT FORMAT:
* Line 1: Ten space-separated integers: N, a, b, c, d, e, f, g, h, and
M
SAMPLE INPUT (file farmoff.in):
2 0 1 5 55555555 0 1 0 55555555 55555555
INPUT DETAILS:
The functions generate weights of 5, 6, 9, 14, 21, and 30 along
with utilities of 0, 1, 8, 27, 64, and 125.
OUTPUT FORMAT:
* Line 1: A single integer representing the lowest sum of the weights
of the N cows with the highest net utility.
SAMPLE OUTPUT (file farmoff.out):
51
OUTPUT DETAILS:
The two cows with the highest utility are cow 5 and 6, and their combined
weight is 21+30=51.
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Problem 8: Job Hunt [Haitao Mao, 2009]
Bessie is running out of money and is searching for jobs. Farmer
John knows this and wants the cows to travel around so he has imposed
a rule that his cows can only make D (1 <= D <= 1,000) dollars in
a city before they must work in another city. Bessie can, however,
return to a city after working elsewhere for a while and again earn
the D dollars maximum in that city. There is no limit on the number
of times Bessie can do this.
Bessie's world comprises P (1 <= P <= 150) one-way paths connecting
C (2 <= C <= 220) cities conveniently numbered 1..C. Bessie is
currently in city S (1 <= S <= C). Path i runs one-way from city
A_i to city B_i (1 <= A_i <= C; 1 <= B_i <= C) and costs nothing
to traverse.
To help Bessie, Farmer John will give her access to his private jet
service. This service features F (1 <= F <= 350) routes, each of
which is a one way flight from one city J_i to a another K_i (1 <=
J_i <= C; 1 <= K_i <= C) and which costs T_i (1 <= T_i <= 50,000)
dollars. Bessie can pay for the tickets from future earnings if she
doesn't have the cash on hand.
Bessie can opt to retire whenever and wherever she wants. Given an
unlimited amount of time, what is the most money that Bessie can
make presuming she can make the full D dollars in each city she can
travel to? Print -1 if there is no limit to this amount.
PROBLEM NAME: jobhunt
INPUT FORMAT:
* Line 1: Five space-separated integers: D, P, C, F, and S
* Lines 2..P+1: Line i+1 contains two space-separated integers that
name a one-way path from one city to another: A_i and B_i
* Lines P+2..P+F+1: Line P+i+1 contains three space-separated integers
that name a one-way jet flight from one city to another and
the price for that flight: J_i, K_i, and T_i
SAMPLE INPUT (file jobhunt.in):
100 3 5 2 1
1 5
2 3
1 4
5 2 150
2 5 120
INPUT DETAILS:
This world has five cities, three paths and two jet routes. Bessie
starts out in city 1, and she can only make 100 dollars in each
city before moving on.
OUTPUT FORMAT:
* Line 1: A single integer representing the most money she can make
while following the law.
SAMPLE OUTPUT (file jobhunt.out):
250
OUTPUT DETAILS:
Bessie can travel from city 1 to city 5 to city 2 to city 3, and
make a total of 4*100 - 150 = 250 dollars.
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