problem-solving

A problem with connected points and determining geometry figures based on points' location analysis

In school we have a really hard problem, and still no one from the students has solved it yet. Take a look at the picture below: http://d.imagehost.org/0422/mreza.gif That's a kind of a network of connected points, which doesn't end and each point has its own number representing it. Let say the numbers are like this: 1-23-456-78910-et...

Problem with splitting private stock market packets in application

I've written a small application that deals with the private stock market. I store all data in one table (to simplify problem) with following columns: ID, TransactionType, Quantity, Numbers From, Numbers Too, Client ID, Date 1, Buy, 100, AB1000, AB1099, 5, 2009-01-30 2, Sell, 100, AB1000, AB1099, 5, 2010-01-01 3, Buy, 40, AB500...

Closest Approach question for math/physics heads

I'm using a Segment to Segment closest approach method which will output the closest distance between two segments of length. Each segment corresponds to a sphere object's origin and destination. The speed is simply from one point, to the other. Closest Approach can succeed even when there won't be a real collision. So, I'm currentl...

Generating all unique combinations for "drive ya nuts" puzzle

A while back I wrote a simple python program to brute-force the single solution for the drive ya nuts puzzle. The puzzle consists of 7 hexagons with the numbers 1-6 on them, and all pieces must be aligned so that each number is adjacent to the same number on the next piece. The puzzle has ~1.4G non-unique possibilities: you have 7! o...

RSA Factorization problem

At class we found this programming problem, and currently, we have no idea how to solve it. The positive integer n is given. It is known that n = p * q, where p and q are primes, p<=q and |q-k*p|<10^5 for some given positive integer k. You must find p and q. Input: 35 1 121 1 1000730021 9 Output: 5 * 7 11 * 11 10007 * 100003 ...

Finding unreachable sections of a 2D map

I don't want you to solve this problem for me, i just want to ask for some ideas. This is the input below, and it represents a map. The 'x' represents land, and the dots - water. So with the 'x' you can represent 'islands' on the map. xxx.x...xxxxx xxxx....x...x ........x.x.x ..xxxxx.x...x ..x...x.xxx.x ...

Looking for ideas how to refactor my (complex) algorithm

I am trying to write my own Game of Life, with my own set of rules. First 'concept', which I would like to apply, is socialization (which basicaly means if the cell wants to be alone or in a group with other cells). Data structure is 2-dimensional array (for now). In order to be able to move a cell to/away from a group of another cells,...

Given two lines on a plane, how to find integer points closest to their intersection?

I can't solve it: You are given 8 integers: A, B, C representing a line on a plane with equation A*x + B*y = C a, b, c representing another line x, y representing a point on a plane The two lines are not parallel therefore divide plane into 4 pieces. Point (x, y) lies inside of one these pieces. Problem: Write a fast algorithm tha...

While programming, what to do when facing with a seemingly unsolvable situation with a time limit?

This is not a technical question, but rather a social and methodical one. I am a computer sciences student and I usually have really tough programming assignments. I don`t know if it is only happening to me but sometimes, particularly when deadline is approaching, i find myself in a harsh situation. I cannot find my mistake in the code o...

Compact a given array problem

Dont know whether this is a duplicate, but this was an interview question asked to me. Given an array of random numbers and -1 placed inbetween, I have to compact the array meaning all the -1s are to be replaced and the final output should be the last valid index with the fresh array. For example. Input: 3 4 -1 -1 -1 5 8 -1 8 Output: 3 ...

What problem does NHibernate solve?

I've seen some jobs that require nhibernate knowledge, as well as numerous questions on stack. I found another question that pointed me to Summer Of NHibernate and I am watching the videos now. However it has no introduction explaining why NHibernate was created and what problem is solves. By looking on wikipedia, I can see vaguely what ...

Can someone recommend a resource/site/book to improve problem solving skills

I am a reasonably experienced developer (.NET, c#, asp.NET etc) but I'd like to hone my problem solving skills. I find that when I come up against a complex problem I sometimes implement a solution that I feel could have been better had I analyzed the problem in a different way. Ideally what I am looking for is a resource of some type t...

Combinatorics grouping problem

I'm looking for an algorithm in c# that solves a combinatorics problem: Assume i have the objects 1,2,3,4 I want to get all possible ways to group these object in multiple groups, that each time contain all objects. Order is not important. Example: <1,2,3,4> <1,2 / 3,4> <1,3 / 2,4> <1,4 / 3,2> <1,2,3 / 4> <1,2,4 / 3> <1,3,4 / 2> <2...

Solving a math problem/expression, which is a string, in PHP

The user can enter a math problem (expression) like 5 + 654, 6 ^ 24, 2!, sqrt(543), log(54), sin 5, sin(50). After some reformatting (e.g. change sin 5 into sin(5)), and doing an eval, PHP gives me the right result: $problem = "5 + 5324"; eval("$result = " . $problem); echo $problem . " = " . $result; However, this is quite unsafe: /...

SelectMany in Linq to entity

I was looking at some examples in microsoft site about linq and I see an example that I need to modify! http://msdn.microsoft.com/en-us/vcsharp/aa336758.aspx#SelectManyCompoundfrom3 public void Linq16() { List customers = GetCustomerList(); var orders = from c in customers from o in c.Orders where o.OrderDate >= new Da...

Good recources on a problem decomposition?

Could you please share some good books, blogs, sites on practical problem decomposition, thanks P.S. Please only practical ones not the scientific/theoretical resources. ...

Need help programming with Mclauren series and Taylor series!

Ok so here's what i have so far: #include <stdio.h> #include <math.h> //#define PI 3.14159 int factorial(int n){ if(n <= 1) return(1); else return(n * factorial(n-1)); } void McLaurin(float pi){ int factorial(int); float x = 42*pi/180; int i, val=0, sign; for(i=1, sign=-1; i<11; i+=2){ sign *= -1; // alternate...

best practices - multiple functions vs single function with switch case

I have a situation where I need to perform several small (but similar) tasks. I can think of two ways to achieve this. First Approach: function doTask1(); function doTask2(); function doTask3(); function doTask4(); Second Approach: // TASK1, TASK2, ... TASK4 are all constants function doTask(TASK) { switch(TASK) { case ...

Problem solving/ Algorithm Skill is a knack or can be developed with practice?

Every time I start a hard problem and if can not figure out the exact solution or can not get started, I get into this never ending discussion with myself, as below: That problem solving/mathematics/algorithms skills are gifted (not that you can learn by practicing, by practice, you only master the kind of problems that you already ha...

Pecking order of pigeons?

I was going though problems on graph theory posted by Prof. Ericksson from my alma-mater and came across this rather unique question about pigeons and their innate tendency to form pecking orders. The question goes as follows: Whenever groups of pigeons gather, they instinctively establish a pecking order. For any pair of pigeons...