[김한기] Week 5 Solutions

3sum/han.exs

@@ -0,0 +1,38 @@
+defmodule Solution do
+  @spec three_sum(nums :: [integer]) :: [[integer]]
+  def three_sum(nums) do
+    length_of_nums = length nums
+    num_index_map = nums |> Enum.with_index |> Map.new
+    frequencies_of_num = nums |> Enum.frequencies()
+    tuple_nums = nums |> List.to_tuple
+    num_indexs_map = nums |>
+      Enum.with_index() |>
+      Enum.group_by(fn {v, _} -> v end, fn {_, i} -> i end)
+
+    Stream.unfold({0, 1}, fn {i, j} ->
+      if j < length_of_nums - 1,
+      do: {{i, j}, {i, j + 1}},
+      else: {{i, j}, {i + 1, i + 2}}
+    end) |>
+      Stream.take_while(fn {i, _} ->
+        i < length_of_nums - 1
+      end) |>
+      Stream.map(fn {i, j} ->
+        a = elem tuple_nums, i
+        b = elem tuple_nums, j
+        c = -(a + b)
+
+        case frequencies_of_num[c] do
+          nil -> nil
+          count when count >= 3 -> [a, b, c] |> Enum.sort()
+          _ ->
+            if num_indexs_map[c] |> Enum.filter(& &1 != i && &1 != j) |> Enum.at(0),
+            do: [a, b, c] |> Enum.sort(),
+            else: nil
+        end
+      end) |>
+      Stream.reject(& &1 == nil) |>
+      Stream.uniq |>
+      Enum.to_list
+  end
+end

encode-and-decode-strings/han.py

@@ -0,0 +1,68 @@
+#!/usr/bin/env python3
+class Solution:
+    """
+    @param: strs: a list of strings
+    @return: encodes a list of strings to a single string.
+    """
+    def encode(self, strs):
+        return '-'.join([
+            '.'.join([
+                str(ord(c))
+                for c in s
+            ])
+            for s in strs
+        ])
+
+    """
+    @param: str: A string
+    @return: decodes a single string to a list of strings
+    """
+    def decode(self, str):
+        return [
+            ''.join([
+                chr(int(c))
+                for c in s.split('.')
+            ])
+            for s in str.split('-')
+        ]
+
+
+# 아래는 간단한 테스트 코드
+import random
+
+def generate_random_string(min_length=5, max_length=20):
+    # Choose a random string length between min_length and max_length
+    string_length = random.randint(min_length, max_length)
+
+    # Define the character categories
+    alphabets = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
+    numbers = '0123456789'
+    hanguls = '가나다라마바사아자차카타파하'
+    emojis = ['😀', '😂', '😉', '😍', '😎', '😭', '😊', '😜', '😢', '😱']
+
+    # Probability of selecting from each category
+    weights = [0.25, 0.25, 0.25, 0.25]
+
+    # Combine all categories into a single list
+    all_chars = list(alphabets + numbers + hanguls) + emojis
+
+    # Select characters based on the weights and create the final string
+    random_chars = random.choices(all_chars, k=string_length)
+    random_string = ''.join(random_chars)
+
+    return random_string
+
+def generate_multiple_random_strings():
+    strings_list = []
+    # Generate a random number of strings, between 1 and 10
+    number_of_strings = random.randint(1, 10)
+
+    for _ in range(number_of_strings):
+        random_string = generate_random_string()
+        strings_list.append(random_string)
+
+    return strings_list
+
+strs = generate_multiple_random_strings()
+print(strs)
+print(strs==Solution().decode(Solution().encode(strs)))

top-k-frequent-elements/han.exs

@@ -0,0 +1,10 @@
+defmodule Solution do
+  @spec top_k_frequent(nums :: [integer], k :: integer) :: [integer]
+  def top_k_frequent(nums, k) do
+    nums |>
+      Enum.frequencies |>
+      Enum.sort_by(fn {_, v} -> v end, :desc) |>
+      Enum.take(k) |>
+      Enum.map(fn {k, _} -> k end)
+  end
+end