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Write a program that takes as input a list of n integers and produces as output the largest difference obtained by subtracting an integer in the list from the one following it
I can think of this using the combination method.
ar = (1..12).to_a
ar.combination(2).max_by { |a,b| b - a }
# => [1, 12]
ar = [1,23,56,11]
# => [1, 23, 56, 11]
ar.combination(2).max_by { |a,b| (b - a).abs }
# => [1, 56]
It seems I misunderstood the line as OP mentioned :
output the largest difference obtained by subtracting an integer in the list from the one following it
Here is the correct one :-
ar = [1,23,56,11]
ar.each_cons(2).max_by { |a, b| (b - a).abs }
# => [56, 11]
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I'm new to rails and I was wondering how I compare the first value of array "a" if it is greater than the first value of array "b"?
Example:
a = [1, 2, 3]
b = [3, 2, 1]
How do I check if a[0] is greater than b[0].
You can use the first method:
a = [1, 2, 3]
b = [3, 2, 1]
a.first > b.first #=> false
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I'm looking for an algorithm to merge/compress lists of unsorted integers in to a single list while maintaining the original lists.
Example
A = [1, 1, 3]
B = [3, 2, 9]
C = [1, 3, 2]
D = [1]
A C
| |
Result[ 1 1 3 2 9 ]
| |
D B
I found lots of results with similar questions but most of them deal with sorted lists or break them up. I'm sure something like this exists but I simply don't know the correct terminology.
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A,B,C are the arrays :
A = {1,2,3,4}
B = {8,1,2,3}
C = {1,2,9,3}
Result is the uncommon values from three arrays
Result = {4,8,9}
Asking for the logic what I can implement ?
There might be some other better answers. But here is the most simple one.
On line 4 I took the Intersection of 3 sets
On line 7 I took the Union of three sets
On line 10 the difference or XOR operation, of Union and intersection
I hope it helps:-
>>> a = {1,2,3,4}
>>> b = {8,1,2,3}
>>> c = {1,2,9,3}
>>> d = a & b & c
>>> print(d)
{1, 2, 3}
>>> e = a | b | c
>>> print(e)
{1, 2, 3, 4, 8, 9}
>>> f = d^e
>>> print(f)
{4, 8, 9}
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Can't understand the difference between select and collect methods. Also want to know when to use each.
Enumerable#collect (or Enumerable#map) returns a result of applying block to each items.
[1, 2, 3, 4].collect { |x| x > 2 }
# => [false, false, true, true]
While Enumerable#select returns an array of filtered items:
[1, 2, 3, 4].select { |x| x > 2 }
# => [3, 4]
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I'm looking for the fastest way to split an array into sub-arrays with different size. The size of every array is driven by a configuration file.
Example:
c = [1,2,3,4,5,6,7,8]
My configuration file:
block
contents: 3
type: ...
scope ...
block
contents: 1
type: ...
scope ...
block
contents: 2
type: ...
scope ...
block
contents: 2
type: ...
scope ...
c.size is equal to the sum of the content number of every block.
I must split my array into 'n' arrays where n is the number of blocks I define in my config file and the size of every array is the number of contents defined in that block.
The result with the given array and config file is:
[1,2,3]
[4]
[5,6]
[7.8]
Any idea with good performance result?
A slight variant of Matt's answer:
If you read the values from the file into:
a = [3,1,2,2]
you can then do this:
a.each_with_object([]) {|e,b| b << c.shift(e)}
#=> [[1, 2, 3], [4], [5, 6], [7, 8]]
c = [1,2,3,4,5,6,7,8]
d = [3,1,2,2]
d.map { |n| c.shift n } # => [[1, 2, 3], [4], [5, 6], [7, 8]]
This destroys the original c.