[rivkode] Week 2

3sum/rivkode.py

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+from typing import List, Tuple, Set
+
+# threeSum3()
+# Time Complexity O(n ^ 2)
+# - when sorting by sorted function(TimSort) for each string it takes O(nlogn)
+# - traversing for loop takes O(n) and check left and right in the while loop at the same time.
+# Space Complexity O(n)
+# - when sorting takes O(1)
+
+
+class Solution:
+    def threeSum(self, nums: List[int]) -> list[tuple[int, ...]]:
+
+        triplets = set()
+        for i in range(len(nums) - 2):
+            for j in range(i + 1, len(nums)):
+                for k in range(j + 1, len(nums)):
+                    if nums[i] + nums[j] + nums[k] == 0:
+                        triplet = [nums[i], nums[j], nums[k]]
+                        triplets.add(tuple(sorted(triplet)))
+
+        return list(triplets)
+
+    def threeSum2(self, nums: List[int]) -> list[tuple[int, ...]]:
+        triplets = set()
+
+        for i in range(len(nums)):
+            seen = set()
+            for j in range(i + 1, len(nums)):
+                res = -(nums[i] + nums[j])
+                if res in seen:
+                    triplet = [nums[i], nums[j], res]
+                    triplets.add(tuple(sorted(triplet)))
+                seen.add(nums[j])
+
+        return list(triplets)
+
+    def threeSum3(self, nums: List[int]) -> list(tuple[int, ...]):
+        triplets = set()
+        nums.sort()
+
+        for i in range(len(nums) - 2):
+            l = i + 1
+            r = len(nums) - 1
+
+            while l < r:
+                res = nums[l] + nums[r] + nums[i]
+                if res > 0:
+                    r -= 1
+                elif res < 0:
+                    l += 1
+                elif res == 0:
+                    triple = (nums[l], nums[r], nums[i])
+                    triplets.add(triple)
+                    l, r = l + 1, r - 1
+                else:
+                    raise Exception
+        return list(triplets)
+
+if __name__ == "__main__":
+    nums = [-1,0,1,2,-1,-4]
+
+
+    solution = Solution()
+    solution.threeSum3(nums)

climbing-stairs/rivkode.py

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+# Time Complexity O(n)
+# - traversing for loop takes O(n)
+# Space Complexity O(n)
+# - appending for loop it takes O(n)
+
+class Solution:
+    def climbStairs(self, n: int) -> int:
+        stage = [1, 2, 3]
+
+        for i in range(3, 45):
+            value = stage[i - 1] + stage[i - 2]
+            stage.append(value)
+
+        return stage[n - 1]
+
+if __name__ == "__main__":
+    solution = Solution()
+    result = solution.climbStairs(5)
+    print(result)
+

valid-anagram/rivkode.py

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+from typing import List
+
+# Time Complexity O(n log n)
+# - when sorting by sorted function(TimSort) for each string it takes O(nlogn)
+# - traversing for loop takes O(n)
+# Space Complexity O(n)
+# - when sorting takes O(n)
+
+class Solution:
+    def isAnagram(self, s: str, t: str) -> bool:
+        s_sorted = sorted(s)
+        t_sorted = sorted(t)
+
+        for i in range(len(s_sorted)):
+            if s_sorted[i] != t_sorted[i]:
+                return False
+        return True
+
+if __name__ == "__main__":
+    solution = Solution()
+
+    s = "nagaram"
+    t = "anagram"
+
+    result = solution.isAnagram(s, t)
+    print(result)