Ruby standard input

Introduction

This time I often use standard input for programming problems, so I'll leave a note. The language used is Ruby.

For strings

When there is only one element per line

Standard input
Tokyo

line = gets
p line

Output result
"Tokyo"

When there are multiple elements in one line

Standard input
Tokyo Osaka Kyoto

line = gets.split(' ')
p line

Output result
["Tokyo", "Osaka", "Kyoto"]

By using the split method, the three elements are stored in the array as separate ones.

When elements exist one by one in multiple lines

Standard input
Tokyo
Osaka
Kyoto

line = readlines
len = line.length
i = 0

while i < len
    line[i] = line[i].chomp
    i += 1
end

p line 

Output result
["Tokyo", "Osaka", "Kyoto"]

A concise way to write the above is to use the map method.

Standard input
Tokyo
Osaka
Kyoto

line = readlines.map(&:chomp)
p line 

Output result
["Tokyo", "Osaka", "Kyoto"]

When there are multiple elements in multiple lines

Standard input
Tokyo Osaka Kyoto
Japan USA China

line = readlines
len = line.length
i = 0

while i < len
    line[i] = line[i].chomp.split(' ')
    i += 1
end

p line

Output result
[["Tokyo", "Osaka", "Kyoto"], ["Japan", "USA", "China"]]

There is also the following as a concise way of writing the above

Standard input
Tokyo Osaka Kyoto
Japan USA China

lines = []
while line = gets
    lines << line.chomp.split(' ')
end
p lines

Output result
[["Tokyo", "Osaka", "Kyoto"], ["Japan", "USA", "China"]]

By setting while line = gets, it will be repeated until all the standard input values are acquired.

Standard input
Tokyo Osaka Kyoto
Japan USA China

lines = readlines(chomp: true).map{|line| line.split(' ')}
p lines

Output result
[["Tokyo", "Osaka", "Kyoto"], ["Japan", "USA", "China"]]

Looking at the output result, the received value is a character string, so if you want to receive a numerical value, do as follows

If you want to receive it numerically

There is only one element per line

Standard input
123

line = gets.to_i
p line

Output result
123

When there are multiple elements in one line

Standard input
1 2 3

line = gets.split(' ')
p line

Output result
["1", "2", "3"]

If this is left as it is, it will be treated as a character string, so use map to convert it to a numeric type array.

Standard input
1 2 3

line = gets.split(' ').map(&:to_i)
p line

Output result
[1, 2, 3]

When there is one element in multiple lines

Standard input
1
2
3

line = readlines.map(&:to_i)
p line 

Output result
[1, 2, 3]

When there are multiple elements in multiple lines

Standard input
1 2 3
4 5 6

lines = []
while line = gets
    lines << line.chomp.split(' ').map(&:to_i)
end
p lines

Output result
[[1, 2, 3], [4, 5, 6]]

Here's how to write more concisely

Standard input
1 2 3
4 5 6

lines = readlines(chomp: true).map{|line| line.split(' ').map(&:to_i)}
p lines

Output result
[[1, 2, 3], [4, 5, 6]]

Finally

I think there are various other methods, so I will update them from time to time.