LeetCode에서 Ruby를 공부해 보았습니다.

LeetCode란?

실제로 출제 된 기술 테스트를 풀 수있는 사이트

카테고리(algo/database/system design...) && 난이도별 등으로 나뉘어진 1000 근처의 문제

Go/Scala/Kotlin과 같은 많은 언어를 사용할 수 있습니다

GAFA 등에서 실제로 출제 된 문제를 게재

구독으로 기업별 문제를 풀 수 있다(테크계의 적책!?)

모바일 버전도 있습니다 (iOS : Leetcode client 등)

자세한 문제 해설 등 매력 가득

English or Chinese!

Tips

문제수가 많습니다만, Problems -> Lists -> Top 100 Liked Questions로 정렬할 수 있어 좋다. 본가의 해답이 준비되어 있지 않은 문제도 있습니다만, Youtube등으로 검색하면 히트 하는 것이 많습니다.

주의: 아래 답변은 불완전한 것을 포함합니다.

#1. TwoSum (easy)

Question:
Given an array of integers, return indices of the two numbers such that they add up to a specific target. You may assume that each input would have exactly one solution, and you may not use the same element twice.
Example:
Given nums = [2, 7, 11, 15], target = 9,
nums[a] + nums[b] = 2 + 7 = target,
return [0, 1].

my_challenge.rb

def two_sum(nums, target)
    nums.each_with_index do |num1, a|
        nums.each_with_index do |num2, b|
          return [a,b] if num1 + num2 == target
        end
    end
    return "Cannot find two_sum"
end

puts two_sum([2, 6, 11, 15], 9)

#7. Reverse Integer (easy)

Question:
Given a 32-bit signed integer, reverse digits of an integer.
Example:
Input: 123
출력: 321

Input: -123
Output: -321

Input: 120
Output: 21

my_challenge.rb

# ignore solution for the case: 32bit
def reverse(x)
    a = x.to_s.chars
    b = []
    i = -1

    while i >= -a.length
        b.push(a[i])
        i -= 1
    end

    if(x > 0)
        return b.join().to_i
    else(x < 0)
        return -b.join().to_i
    end 
end

#412. Fizz Buzz (easy)

Question:
Write a program that outputs the string representation of numbers from 1 to n.
But for multiples of three it should output “Fizz” instead of the number and for the multiples of five output “Buzz”.
For numbers which are multiples of both three and five output “FizzBuzz”.
Example:
n = 15,

Return:
[
"1",
"2",
"Fizz",
"4",
"Buzz",
"Fizz",
"7",
"8",
"Fizz",
"Buzz",
"11",
"Fizz",
"13",
"14",
"FizzBuzz"
]

my_challenge.rb

def FizzBuzz(n)
    i = 0
    n.times do |i|
        i += 1
        if (i % 3 == 0 && i % 5 == 0)
            puts "FizzBuzz"
        elsif (i % 3 == 0)
            puts "Fizz"
        elsif (i % 5 == 0)
            puts "Buzz"
        else
            puts i
        end
    end
end

#136. Single Number (easy)

Question:
Given a non-empty array of integers, every element appears twice except for one. Find that single one.
Example:
Input: [2,2,1]
Output: 1

Input: [4,1,2,1,2]
Output: 4

my_challenge.rb

def single_number(nums)
    i = 0
    a = []
    while i < nums.length
        if (a.include?(nums[i]))
            a.delete(nums[i])
        else
            a.push(nums[i])
        end
        i += 1
    end
    puts a
end

#139. Word Break (medium)

Question:
Given a non-empty string s and a dictionary wordDict containing a list of non-empty words, determine if s can be segmented into a space-separated sequence of one or more dictionary words.
Example:
Example 1:

Input: s = "leetcode", wordDict = ["leet", "code"]
Output: true

Input: s = "applepenapple", wordDict = ["apple", "pen"]
Output: true

Input: s = "catsandog", wordDict = ["cats", "dog", "sand", "and", "cat"]
Output: false

my_challenge.rb

#11 / 36 test cases passed.

def word_break(s, word_dict)
    a = s.to_s.chars
    b = []
    i = 0
    while i < s.length
    b.push(a[0..i].join(''))
    b.push(a[i+1..s.length].join(''))
    i += 1
    end

    if (b.include?(word_dict[0] && word_dict[1]))
        return true
    end

end

Ruby Basics Memo

루프

#while
x = 0
while x<40
    x+=1  #can't use ++,--
    if (x%2) != 0
        puts x
    end
end


#for_in
nums = [21,54,32,6,4,23,5]
i = 0

for num in nums 
    i+=1
    puts "##{i} is #{num}"
end


#each
nums.each do |num|  #or (0..nums.length).each
    puts "#{num} by another way"
end


#multi loop
array = [2, 7, 11, 15]
target = 9

array.each do |arr1, a|
    array.each do |arr2, b|
        return puts "#{arr1} and #{arr2}" if arr1 + arr2 == target
    end
end

function

x = 25
def tow_nums(nums)
    x = 10
    return (nums[0] + nums[1]).to_s + " and the x is #{x}" # return x=10
end

puts tow_nums([23,234])

클래스

class Pokemon 
    attr_accessor :name, :hp, :attack

    def initialize(name, hp, attack)
        @name = name; @hp = hp; @attack = attack;   
    end

    def bark
        return "bowowow"
    end
end

pikachu = Pokemon.new("pika","100","50")
puts pikachu.name  #pika
puts pikachu.bark()  #bowowow