Complexity is the analysis of how the time and space requirements of an algorithm vary according to the size of the input. Use this tag for reviews where the "Big O" is a concern.
3
votes
1answer
26 views
Construct KD-Tree in Java
I want to construct KD-Tree from unsorted List of points in the plane (i.e. 2-KD-Tree). To do so I used the method from Wikipedia: http://en.wikipedia.org/wiki/Kd-tree#Construction This is my code:
...
5
votes
2answers
68 views
Time Limit Exceeded with Segment Tree data structure
I am trying to solve this problem
Chef Ceil has some matchsticks in his kitchen.
Detail of matchsticks:
There are N matchsticks in total. They are numbered from to 0 to N-1
inclusive. ...
6
votes
1answer
83 views
Russian doll envelops
Interview question from the interwebz
You have a set of envelopes of different widths and heights. One
envelope can fit into another if and only if both the width and height
of one envelope ...
8
votes
1answer
82 views
Finding largest subset of line segments that don't intersect
I completed a challenge of codeeval called BayBridges. It can be found here. I have uploaded my code on GitHub here.
In summary, the challenge is to take a list of line segments, each specified by ...
2
votes
1answer
38 views
Two squares or not two squares - constant time optimization
I have been trying to solve this problem, and after a bit of googling, I realised a \$O(\sqrt{n})\$ time complexity works fine (though the algorithm suggested is different from that I have used). My ...
5
votes
3answers
193 views
Psycho and ordinary numbers
The problem statement can be found here. In short, here's what the problem is about:
You're given a set of numbers and you need to find whether the the numbers are ordinary or psycho. For a number ...
0
votes
0answers
26 views
Proving a conjecture given a set of clauses - calculating complexity
I have written this Perl program to prove a conjecture given a set of clauses. I've actually posted some code from it on here in another question.
This time its all done and I've made it as fast as ...
28
votes
11answers
3k views
Searching in an array in less than O(n) time
I have an array where each element is either one less or one greater than the preceding element \$\{x_i = x_{i-1} \pm 1\}\$. I wish to find an element in it in less than \$O(n)\$ time. I've ...
6
votes
1answer
186 views
Simplify function to sum the absolute value of the difference between all pairs of elements of a sorted array
Given a sorted array of N elements, I need to find the absolute sum of the differences of all elements.
Given 4 elements (1, 2, 3 and 4):
|1-2|+|1-3|+|1-4|+|2-3|+|2-4|+|3-4| = 10
Here is my ...
5
votes
1answer
86 views
Calculate difference of indices
The challenge is to reconstruct an n-digit number using the following information:
On each step, you choose an index x from 1 to n. For all indices y (y
< x), you calculate the difference by ...
8
votes
3answers
117 views
Longest 'balanced' substring
I was given a task where given a string of '0's and '1's, return the longest substring where the count of '0's and '1's are equal. I was told also that the code should be O(n) and space O(1).
Below ...
6
votes
3answers
276 views
Performance analysis of 3 digits sum
I have a method that finds 3 numbers in an array that add up to a desired number.
...
10
votes
3answers
1k views
Find all paths from source to destination
Given a directed connected graphs, find all paths from source to destination.
Looking for code review, optimizations and best practices. Also need help figuring out complexity, which in my best ...
7
votes
1answer
135 views
Determine total number of ways of reaching a destination
Question:
One of Scotland Yard’s most wanted criminal (Mister X) is on the run
and needs to reach a certain destination safely. There are three modes
of transport available for him - By ...
5
votes
2answers
84 views
Genomic Range Query
Recently I worked on one of the Codility Training - Genomic Range Query (please refer to one of the evaluation report for the detail of this training).
The proper approach for this question is using ...
10
votes
5answers
417 views
Refactoring my problem-solution to reduce complexity
I need some help refactoring my solution to the problem below:
Problem Statement
An Association of Computer Scientists meets on a weekly basis. There is a certain number of seats in the meeting ...
5
votes
2answers
121 views
9
votes
2answers
472 views
'Team Split' problem
Below is my solution for this 'Team Split' problem.
In summary, the problem is to find relative strength of 2 teams by finding the difference between their total strength (individual strengths can be ...
5
votes
1answer
1k views
Stable radix sort in-place using O(1) space
I am trying to implement a stable radix sort in place with O(1) space. I've seen Wikipedia, and I notice the C implementation is using a temporary variable to hold the sorted value for each pass, and ...
2
votes
2answers
1k views
Fish Food Chain O(N)
I understand that if you don't know the trick, it's not easy create a solution with a complexity of O(N). However, I would like to ask you how to solve this tricky question:
You are given two ...
3
votes
1answer
131 views
Big-O complexity calculation for a merge and sort function
I have the following code which basically takes a list of sorted integer arrays and merges them together removing the duplicates.
I have tried to do the complexity analysis and came to a rough ...
3
votes
0answers
252 views
Nonogram puzzle solution space
I've written some code to brute-force enumerate the solution space of nonogram puzzles up to a certain size. It does a good job up to the first ~4 billion puzzles, but I run out of disk space to store ...
5
votes
1answer
166 views
Reducing complexity of method
I'm trying to reduce the complexity of some methods, and I'm not exactly sure what approach to take. I'm currently building a PHP wrapper for a REST API, and the main problematic class is here:
...
1
vote
1answer
131 views
Performance issue of LFU-like web caching replacement algorithm
I have implemented a simulation program that runs LRU and another web caching algorithm called Sliding Window LFU. I want to compare them both in terms of the hit rate and their run time. SW-LFU works ...
6
votes
2answers
1k views
Permutation of given string
I am reading a book on DSA, and the author explains how to generate the permutation of strings using recursion. I want to know if there are better ways of doing the same, unless this is the best ...
1
vote
0answers
139 views
Space and time complexity of operation on lists
I'm new to programming and even more new to Haskell. Below is a little tid-bit I wrote that operates on a bunch of lists. I am wondering if someone would be kind enough to walk through the function ...
4
votes
1answer
86 views
Is this an efficient merge sort implementation with regards to average time complexity in Big-O notation?
Is my below merge sort implementation in O(n log n)? I am trying to implement a solution to find k-th largest element in a given integer list with duplicates with O(N*log(N)) average time complexity ...
7
votes
4answers
3k views
Checking if three numbers sum to a given number
I'm working on the following interview practice problem, and got the following solution, which runs in worst case n! time (best case constant), and I'm trying to ...
3
votes
0answers
45 views
TLE for SPOJ Upper Right King
I am solving this problem on SPOJ Upper Right King (Hard).
I've written a solution in Python with a time complexity of O(n(logm)2). But it's showing TLE. Can anyone help me out with this?
For more ...
2
votes
2answers
1k views
8
votes
3answers
237 views
Can anyone make my O(n^3) function more efficient, or offer suggestions to make handling it more efficient?
I'm trying to devise a way to calculate the mean differences (the absolute average differences between any two values in a set), of sub-arrays (starting from arbitrary indices) in an ...
2
votes
1answer
54 views
Given set of cubes can we get a given word?
Given some cubes, can cubes be arranged such that an input word can be formed from the top view of the cubes?
For example: assume an imaginary cube with only 3 surfaces where ...
3
votes
2answers
309 views
Not getting Log(n) performance from quadtree
Here is my QuadTree class and node.
The problem is really with Querying.
In my game, I have a city which can have n * n streets (randomly generated).
And each street has buildings.
What I do is put ...
3
votes
5answers
373 views
count all array[index] == index occurrences
The method foo gets a sorted list with different numbers as a parameter and returns the count of all the occurrences such that: ...
4
votes
1answer
85 views
Using Guava to reduce code complexity (and possibiliy to improve readability) of null check and assign default value
Below is my java code with some complexity,
...
1
vote
3answers
80 views
Find all consecutive sequences in an ordered set
I have the following set. a = [1,2,3,4,5] and i want to find all of the following sequences of consecutive elements:
...
6
votes
4answers
215 views
Reduce complexity of state machine method
I've asked Code Climate to generate metrics for the ftpd Ruby gem. It correctly identified the God class; I know what to do about that. But one of the smaller classes has me stumped. This is ...
