[kayden] Week 05 Solutions

3sum/kayden.py

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+class Solution:
+
+    # 해시맵
+    # 시간복잡도: O(N^2)
+    # 공간복잡도: O(N)
+    def threeSum(self, nums: List[int]) -> List[List[int]]:
+        n = len(nums)
+        nums.sort()
+
+        check = {}
+        for idx, num in enumerate(nums):
+            check[num] = idx
+
+        answer = set()
+        for i in range(n-2):
+            if nums[i] > 0:
+                break
+            if i > 0 and nums[i] == nums[i-1]:
+                continue
+            for j in range(i + 1, n):
+                target = -(nums[i] + nums[j])
+                if not check.get(target, None):
+                    continue
+                if j >= check[target]:
+                    continue
+
+                answer.add((nums[i], nums[j], target))
+
+        return list(answer)
+
+    # 투포인터
+    # 시간복잡도: O(N^2)
+    # 공간복잡도: O(N)
+    def threeSum2(self, nums: List[int]) -> List[List[int]]:
+        n = len(nums)
+        nums.sort()
+
+        answer = set()
+        for i in range(n-2):
+            if nums[i] > 0:
+                break
+            if i > 0 and nums[i] == nums[i-1]:
+                continue
+            l, r = i+1, n-1
+            while l<r:
+                if nums[l] + nums[r] == -nums[i]:
+                    answer.add((nums[i], nums[l], nums[r]))
+                    l += 1
+                    r -= 1
+
+                if nums[l] + nums[r] < -nums[i]:
+                    l += 1
+
+                if nums[l] + nums[r] > -nums[i]:
+                    r -= 1
+
+        return list(answer)

best-time-to-buy-and-sell-stock/kayden.py

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+# 시간복잡도: O(N)
+# 공간복잡도: O(1)
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+
+        answer = 0
+        cur = float(inf)
+        for price in prices:
+            if cur < price:
+                answer = max(answer, price - cur)
+
+            if price < cur:
+                cur = price
+
+        return answer

group-anagrams/kayden.py

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+# 시간복잡도: O(N*AlogA) A: 0<= strs[i]의 길이 <= 100
+# 공간복잡도: O(N)
+class Solution:
+    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
+        groups = {}
+        for anagram in strs:
+            key = str(sorted(anagram))
+            groups.setdefault(key, []).append(anagram)
+
+        return list(groups.values())