[sun] WEEK 5 solution

3sum/sun912.py

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+"""
+    TC: O(n^2)
+    SC: O(1)
+"""
+
+class Solution:
+    def threeSum(self, nums: List[int]) -> List[List[int]]:
+        result = set()
+        nums.sort()
+
+        for i in range(len(nums)-2):
+            left,right = i+1, len(nums)-1
+            while left < right:
+                three_sum = nums[i]+nums[left]+nums[right]
+
+                if three_sum < 0:
+                    left += 1
+                elif three_sum > 0:
+                    right -= 1
+                else:
+                    result.add((nums[i], nums[left], nums[right]))
+                    left,right = left+1, right-1
+
+        return list(result)
+

best-time-to-buy-and-sell-stock/sun912.py

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+"""
+TC: O(n)
+SC: O(1)
+"""
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+        max_profit= 0
+        l = 0
+        r = 1
+
+        while r < len(prices):
+            if prices[l] < prices[r]:
+                profit = prices[r] - prices[l]
+                max_profit = max(max_profit, profit)
+
+            else:
+                l = r
+            r +=1
+        return max_profit
+
+

group-anagrams/sun912.py

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+"""
+    TC: O(m*n)
+    SC: O(26*n) -> O(n)
+"""
+
+from collections import defaultdict
+
+class Solution:
+    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
+        result = defaultdict(list)
+
+        for word in strs:
+            count = [0] * 26
+
+            for c in word:
+                count[ord(c)-ord("a")] += 1
+            result[tuple(count)].append(word)
+
+        return result.values()