[hi-rachel] WEEK 01 solutions

contains-duplicate/hi-rachel.py

@@ -0,0 +1,28 @@
+"""
+https://leetcode.com/problems/contains-duplicate/
+
+Given an integer array nums,
+return true if any value appears at least twice in the array,
+and return false if every element is distinct.
+
+TC: O(n)
+SC: O(n)
+"""
+
+from typing import List
+
+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        seen = set()
+
+        for num in nums:
+            if num in seen:
+                return True
+            else:
+                seen.add(num)
+        return False
+
+
+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        return len(set(nums)) != len(nums)

top-k-frequent-elements/hi-rachel.py

@@ -1,11 +1,19 @@
-# 가장 자주 등장한 상위 K개의 문자 배열 반환
-# O(n log n) time, O(n) space
+"""
+https://leetcode.com/problems/top-k-frequent-elements/
+
+Given an integer array nums and an integer k, return the k most frequent elements.
+You may return the answer in any order.
+
+TC: O(n log n)
+SC: O(n)
+"""
 
 from collections import defaultdict
+from typing import List
 
 class Solution:
     def topKFrequent(self, nums: List[int], k: int) -> List[int]:
-        numdict = defaultdict(int);
+        numdict = defaultdict(int)
 
         for num in nums:
             numdict[num] += 1
@@ -15,3 +23,14 @@ def topKFrequent(self, nums: List[int], k: int) -> List[int]:
         keys = list(sort_dict)
 
         return keys[:k]
+
+# heapq 풀이
+from collections import Counter
+import heapq
+
+class Solution:
+    def topKFrequent(self, nums: List[int], k: int) -> List[int]:
+        counter = Counter(nums)
+        return heapq.nlargest(k, counter.keys(), key=counter.get)
+
+

two-sum/hi-rachel.py

@@ -1,25 +1,17 @@
 """
-처음 풀이
-O(N^2) time, O(N) space
-"""
+https://leetcode.com/problems/two-sum/
 
-# class Solution:
-#     def twoSum(self, nums: List[int], target: int) -> List[int]:
-#         result = []
-#         for i in range(len(nums)):
-#             rest = target - nums[i]
-#             rest_nums = nums[i+1:]
-#             if rest in rest_nums:
-#                 result.extend([i, rest_nums.index(rest)+i+1])
-#                 break
-#         return result
-
+Given an array of integers nums and an integer target,
+return indices of the two numbers such that they add up to target.
+You may assume that each input would have exactly one solution, and you may not use the same element twice.
+You can return the answer in any order.
 
-"""
 개선 코드
 O(N) time, O(N) space
 """
 
+from typing import List
+
 class Solution:
     def twoSum(self, nums: List[int], target: int) -> List[int]:
         indices = {}
@@ -31,6 +23,24 @@ def twoSum(self, nums: List[int], target: int) -> List[int]:
                 return [i, j]
             indices[v] = i
 
+
+"""
+처음 풀이
+O(N^2) time, O(N) space
+"""
+
+# class Solution:
+#     def twoSum(self, nums: List[int], target: int) -> List[int]:
+#         result = []
+#         for i in range(len(nums)):
+#             rest = target - nums[i]
+#             rest_nums = nums[i+1:]
+#             if rest in rest_nums:
+#                 result.extend([i, rest_nums.index(rest)+i+1])
+#                 break
+#         return result
+
+
 # JS 풀이
 # /**
 #  * @param {number[]} nums