OJ Board

I think you used the algorithm I suggested ^_^

I just posted to say this: let be bincoeff(n,k) the binomial coefficient of n elements of class k, we have:

bincoeff(n,0) = 1
bincoeff(n,n) = 1

otherwise:

bincoeff(n,k) = bincoeff(n-1,k-1) + bincoeff(n-1,k)

Don't use factorials, just use DP ...

I solved Clocks (IOI 1994) and it's easily solvable with a breadth-first search (imagine every configuration is a node and every move is an edge). Otherwise, because there are only 4^9 possible configurations, do exaustive search.

Ciao
Ale

This kind of errors are born when you forget to reset some variable. I didn't read the code (I'm tired now ^_^) but try to check for it.

But excuse me, can't you write plainer code? I think it's not a good habit to merge two loop in one. *Almost* all the problems I did were straightforward to write ...

Excuse me if this reply is very late; last moths I had things to do and I didn't visited the forum.

An Index Tree is a binary tree with every node "controlling" a certain interval, and its children control the two halves of the interval. Example: a node controls interval [1,1000], its left son ...

I'd like to know if some poster has solved this problem - it's a IOI 1997 problem, but the USACO contains an harder version in Section 5.5.

I can't find the error in my program. It produces the following output for test case 9:


rincewind could scream for help in thirty four la?guages


where ...

Oh, yes... For my high school final exam I presented a work about NP-completeness, and now I remember Hamiltonian cycle is NP-complete of course!

F**k (the problem, not you Larry )

I propose you a problem about cycles on graphs.

Given an undirected unweighted graph and two nodes A and B, I've got to find a path from A to B and then a path from B to A. I can't visit a node more than once (with the exception of node A, that must be visited at the beginning and at the end). I ...

Wow, I got it right!

Just see the "Network Flow" text at the USACO training program... Near the end you can find the "sample problems", and there is Telecowmunication, with the method I described!

Can you do me a favor, for gratitude ? :)
How can I solve "All Latin Squares", section 5.1 ? You're ...

Maybe I'm completely wrong, now I write my first ideas...

1. Assign edges the weight INFINITY
2. Double the nodes and connect them with a ghost-edge of weight 1
3. Find minimum cut (running maximum flow)

Don't bother me if I'm saying a stupid thing, now I'm tired!

For large numbers you can use probabilistic primality testing. This test give result with a certain % of probability to be correct, but with "small" numbers (with less of 500 ciphers, and such numbers aren't big for numbers theorists) it's OK.

But I don't know where you can see the probabilistic ...

Simple solution: throw Windows out of the window and install Linux! I used Windows for years, now I think a true programmer can't bear with its lack of trasparence. Linux is full of instruments and utilities for a programmer.

I just use gcc/gdb/gprof from the shell...

(Sorry if I made some ...

I understand it's a backtracking search, but I just can't see how to prune the search...

Can you give me some advice?

Can someone help me about this problem? I found it at the USACO website in section 4.3. Don't be afraid from the lenght of the statement of the problem, the second half is a little bit of explanation.

Thanks a lot.

**********
Cowcycles
Originally by Don Gillies

[International readers should ...

I heard about adhoc problems,, but how do i know when a problem belong to this category ??
All programming contests problems can be reduced to a few types of problems, mainly:

Dynamic Programming
Greedy
Complete Search
Flood Fill
Shortest Path
Recursive Search Techniques
Minimum Spanning ...

These numbers are also called BigNums. You must implement the operations all by yourself: for further information see "Programming Challenges" by Skiena-Revilla, chapter 5.