i bet you are stuck on Closed Fences, which is a b*tch... i dont see you why have to stick to USACO
try acm.uva.es or www.topcoder.com they both have lots of practice problems and online judge. i try to stay off those questions that require a specific algorithm such is Dijkstra's or Floyd's shortest paths
here is 3 more from section 2:
Quote: Stringsobits
Kim Schrijvers
Consider an ordered set S of strings of N (1 <= N <= 31) bits. Bits, of course, are either 0 or 1.
This set of strings is interesting because it is ordered and contains all possible strings of length N that have L (1 <= L <= N) or fewer bits that are `1'.
Your task is to read a number I (1 <= I <= sizeof(S)) from the input and print the Ith element of the ordered set for N bits with no more than L bits that are `1'.
PROGRAM NAME: kimbits
INPUT FORMAT
A single line with three space separated integers: N, L, and I.
SAMPLE INPUT (file kimbits.in)
5 3 19
OUTPUT FORMAT
A single line containing the integer that represents the Ith element from the order set, as described.
SAMPLE OUTPUT (file kimbits.out)
10011
Quote:
Money Systems
The cows have not only created their own government but they have chosen to create their own money system. In their own rebellious way, they are curious about values of coinage. Traditionally, coins come in values like 1, 5, 10, 20 or 25, 50, and 100 units, sometimes with a 2 unit coin thrown in for good measure.
The cows want to know how many different ways it is possible to dispense a certain amount of money using various coin systems. For instance, using a system of {1, 2, 5, 10, ...} it is possible to create 18 units several different ways, including: 18x1, 9x2, 8x2+2x1, 3x5+2+1, and many others.
Write a program to compute how many ways to construct a given amount of money using supplied coinage. It is guaranteed that the total will fit into both a signed long long (C/C++) and Int64 (Free Pascal).
PROGRAM NAME: money
INPUT FORMAT
The number of coins in the system is V (1 <= V <= 25).
The amount money to construct is N (1 <= N <= 10,000). Line 1: Two integers, V and N
Lines 2..: V integers that represent the available coins (no particular number of integers per line)
SAMPLE INPUT (file money.in)
3 10
1 2 5
OUTPUT FORMAT
A single line containing the total number of ways to construct N money units using V coins.
SAMPLE OUTPUT (file money.out)
10
haha, try an IOI problem 
Quote:
Sorting a Three-Valued Sequence
IOI'96 - Day 2
Sorting is one of the most frequently performed computational tasks. Consider the special sorting problem in which the records to be sorted have at most three different key values. This happens for instance when we sort medalists of a competition according to medal value, that is, gold medalists come first, followed by silver, and bronze medalists come last.
In this task the possible key values are the integers 1, 2 and 3. The required sorting order is non-decreasing. However, sorting has to be accomplished by a sequence of exchange operations. An exchange operation, defined by two position numbers p and q, exchanges the elements in positions p and q.
You are given a sequence of key values. Write a program that computes the minimal number of exchange operations that are necessary to make the sequence sorted.
PROGRAM NAME: sort3
INPUT FORMAT
Line 1: N (1 <= N <= 1000), the number of records to be sorted
Lines 2-N+1: A single integer from the set {1, 2, 3}
SAMPLE INPUT (file sort3.in)
9
2
2
1
3
3
3
2
3
1
OUTPUT FORMAT
A single line containing the number of exchanges required
SAMPLE OUTPUT (file sort3.out)
4
|
)