[jinah92] Week 2

3sum/jinah92.py

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+# 공간복잡도 : O(1), 시간복잡도 : O(N^2)
+class Solution:
+    def threeSum(self, nums: List[int]) -> List[List[int]]:
+        three_sums = set()
+        nums.sort()
+
+        for i in range(len(nums)-2):
+            low, high = i + 1, len(nums)-1
+            while low < high:
+                three_sum = nums[i] + nums[high] + nums[low]
+                if three_sum < 0:
+                    low += 1
+                elif three_sum > 0:
+                    high -= 1
+                else:
+                    three_sums.add((nums[i], nums[high], nums[low]))
+                    low, high = low+1, high-1
+
+        return list(three_sums)
+

climbing-stairs/jinah92.py

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+# 공간복잡도: O(1), 시간복잡도: O(n)
+class Solution:
+    def climbStairs(self, n: int) -> int:
+        if n < 3:
+            return n
+
+        prev, curr  = 1, 2
+        for num in range(3, n+1):
+            prev, curr = curr, prev + curr
+
+        return curr

valid-anagram/jinah92.py

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+# 공간복잡도: O(n), 시간복잡도: O(n)
+class Solution:
+    def isAnagram(self, s: str, t: str) -> bool:
+        char_set_1, char_set_2 = {}, {}
+
+        for ch in s:
+            char_set_1[ch] = 0 if ch not in char_set_1 else char_set_1[ch] + 1
+
+        for ch in t:
+            char_set_2[ch] = 0 if ch not in char_set_2 else char_set_2[ch] + 1
+
+        # dictionary의 모든 요소 종류와 개수가 일치해야 함
+        return char_set_1 == char_set_2
+