[Ruby] Exclude duplicate elements with the uniq method.

This is a personal memo.

You can use the uniq method to eliminate duplicate elements.

--Non-destructive processing. --Using blocks, you can compare after processing each element --In case of duplication, the first element remains. (Delete the element behind)

For arrays

`python`


arr = [1, 4, 5, 3, 5, 6, 1, 3, 2, 2, 1, 1, 1]
arr.uniq

=> [1, 4, 5, 3, 6, 2]


##Non-destructive confirmation
p arr
=> [1, 4, 5, 3, 5, 6, 1, 3, 2, 2, 1, 1, 1]

** ▼ Processed value ** You can use blocks to compare processed values. It is the corresponding original value that is deleted. (* Not after processing)

・object.uniq{|variable|processing}

For example, for an element containing a character string, use to_s to make all the elements into a character string and then compare them.

`python`


arr1 = [1, 3, 2, "2", "3", 1]

arr1.uniq{|i| i.to_s}
=> [1, 3, 2]

Original value	1	3	2	"2"	"3"	1
After treatment	"1"	"3"	"2"	"2"	"3"	"1"
Remaining elements	○	○	○	×	×	×

Therefore, the output will be the original value [1, 3, 2] corresponding to the first one without duplication.

## For objects You can also delete elements with duplicate values in an object.

・object.uniq{|Variable 1,Variable 2|processing}

--Block is required --Two variables are required. The key is entered in variable 1 and the value is entered in variable 2. --Since the output will be an array, use to_h to return it to an object (symbol).

When making a symbol

`python`


obj = {:a=>1, :b=>2, :c=>3, :d=>2, :f=>3}
obj2 = obj.uniq{|x,y| y}
=> [[:a, 1], [:b, 2], [:c, 3]]}

obj2.to_h
=> {:a=>1, :b=>2, :c=>3}

### When making a hash If you want to make it a hash, apply `to_s` to the key in the block of the` to_h` method to make it a string.

`python`


obj = {:a=>1, :b=>2, :c=>3, :d=>2, :f=>3}

obj.uniq{|x,y| y}.to_h{|k ,v| [k.to_s, v]}
=> {"a"=>1, "b"=>2, "c"=>3}