# Tag Info

Accepted

### Get all combinations of selecting k elements from an n-sized array

Binomial coefficient $\binom{n}{k}$ is growing too fast (with $n$) to keep a list of all combinations in memory. I would suggest to use yield return instead. ...
• 922
Accepted

### List all possible permutations from a python dictionary of lists

The tool you need here is itertools.product: ...
• 49.7k

### Determine if one string is a permutation of the another

I would say yes, use an array. Arrays afford very good memory locality, which is good for cache performance. They essentially are the most basic and efficient hash map if the key is the index. You ...
• 6,006
Accepted

### Find the total number of ways W, in which a sum S can be reached in N throws of a dice

1. Review The sum $s=0$ can be reached in $n=0$ throws in exactly one way, but: ...
• 49.7k
Accepted

### Determine if one string is a permutation of the another

Comparing two maps is linear, so that's not a big problem. I don't think you've made particularly good use of maps though. As I see it, you have two choices. You could use an ...
• 33.6k
Accepted

### A beautiful and easy way of permutation with recursion

The simpler code would look something like this: ...
• 33.6k

### Generating all combinations of an array

In this case, a non-recursive solution is easier to understand, IMHO: ...
Accepted

### On Knuth's "Algorithm L" to generate permutations in lexicographic order

Optimising the functional approach Iterative vs functional approach: Is it possible to use the (existing) functional methods without losing performance? I don't think it's possible to use the ...
• 433
Accepted

### Generating Permutations in Python

Python has so many neat stuff to help you with this one, I feel alot can be rewritten: I did a lot of C++ and miss std::swap(..) Luckily you can swap really easy in python For instance the swap ...
• 11.6k
Accepted

### Earliest time frog can jump to the other side of a river in C#

Readability The code needs more spacing. Considering the comments, the indentation and the ifs, it's hard to read without some good old empty lines. Use brackets when using conditions, especially if ...
• 12.4k

### Project Euler #15: counting paths through a 20 × 20 grid

#include <cstdio> If your goal is to write C++, you're really off to a bad start using the C standard I/O library. ...
• 12.4k

### Generate Letter Combinations of a Phone Number

You can set the keypad lookup as a constant instead of computing it dynamically. Setting it up as constant makes it clearer that what your intent is. ...
• 8,726

### HackerRank: Electronics Shop

early pruning This is very nice: // delete any that are over our budget Doing it before sorting can slightly speed the sorting operation. I say slightly ...
• 32.4k

### Print sums of all subsets

Preface This is great code. Your solution is more than $10^{42}$ times nicer than the given solutions on the linked page that promote crap like ...
• 9,570
Accepted

### LINQ for generating all possible permutations

English language These are relatively minor issues, but fixing them might help other people to use / maintain your code. The verb corresponding to permutation is permute. I'm pretty sure that ...
• 24.1k
Accepted

### Print all "balanced" sequences of 'A' and 'B'

Refactor to use functions Try to avoid boolean variables. Pseudocode like: ...
• 3,948
Accepted

### Sequence-based enumeration of permutations in lexicographic order

Performance I'm not particularly surprised that the version of permutations(of:) which uses AnySequence and ...
• 433
Accepted

### Maximum sub-array of non-negative numbers

1. Bugs maxset returns the wrong answer for some inputs. For example: >>> maxset([2, 1, -1, 1, 3]) [2, 1] The ...
• 49.7k

### Refactor the code which performs "cross-product", "reduce", "product of list" and "sum of list"

One immediate improvement is realizing that for e.g the input 14 7, all combinations like x x x x x x 9 and above can never sum ...
• 41k

### Find all combinations of length 3 whose sum is divisible by a given number

Time complexity of iterating through all the combinations is O(n³). We can solve it in O(n²) by using the fact that if you know 2 numbers out of 3, you know exactly ...
• 2,249

### Generating Permutations in Python

Are you allowed to use standard library functions? If so, why not just use itertools.permutations(): ...
• 4,500
Accepted

### Project Euler #15: counting paths through a 20 × 20 grid

Why are you using unsigned short? I presume the answer is somewhere along the lines of worrying about memory usage. There isn't a problem with that, but given that ...
• 6,006

### Generating the powerset in C

I'll just work through this from the top: #include <stdio.h> #include <stdlib.h> #include <string.h> Looks good; we need these. ...
• 78.7k

### HackerRank: Electronics Shop

General Guidelines You have coded everything in a single class Program. Take advantage of the fact C# is an object oriented language. Create at least one custom ...
• 13.9k
Accepted

### HackerRank: Electronics Shop

3 good answers already, but there's more! I don't like that you modify the array you are given. This sort of thing would need to be documented, and generally creates confusion for all. You don't need ...
• 7,431

### LINQ for generating all possible permutations

Using line breaks and {} in code is not a crime :-P Only because we have the nice => doesn't mean we have to use it ...
• 44.3k
Accepted

### Codility's Permutation Check in C#

One of the unfortunate things you'll notice about coding challenges is that the requirements often force you to write code that isn't ideal. I'm going to call these out, even though in this case they'...
• 1,026