[EGON] Week 4 Solutions

longest-consecutive-sequence/EGON.py

@@ -0,0 +1,66 @@
+from typing import List
+from unittest import TestCase, main
+
+
+class Solution:
+    def longestConsecutive(self, nums: List[int]) -> int:
+        return self.solveWithDict(nums)
+
+    """
+    Runtime: 486 ms (Beats 40.61%)
+    Time Complexity:
+        - nums 배열 조회하며 연산에 O(n)
+        - 크기가 n인 node_dict.items()을 조회, visited에 의해 각 노드당 한 번만 방문,
+            - visited가 set이므로 갱신 및 확인에 O(1)
+            - 2개 항에 대해 max 연산하므로 O(2)로, 총 O(n)
+        > O(n) + O(n) ~= O(n)
+
+    Memory: 44.62 MB (Beats 5.00%)
+    Space Complexity: O(n)
+        - value가 크기 2짜리 배열이고 key가 최대 n인 dict 변수 사용에 O(2n)
+        - 최대 크기가 n인 visited 사용에 O(n)
+        > O(2n) + O(n) ~= O(n)
+    """
+    def solveWithDict(self, nums: List[int]) -> int:
+        node_dict = {}
+        for num in nums:
+            curr_node = [num, num]
+            if num - 1 in node_dict:
+                prev_node = node_dict[num - 1]
+                curr_node[0] = prev_node[0]
+                prev_node[1] = curr_node[1]
+            if num + 1 in node_dict:
+                post_node = node_dict[num + 1]
+                curr_node[1] = post_node[1]
+                post_node[0] = curr_node[0]
+            node_dict[num] = curr_node
+
+        max_length = 0
+        visited = set()
+        for key, (prev_key, post_key) in node_dict.items():
+            while prev_key not in visited and prev_key in node_dict:
+                visited.add(prev_key)
+                prev_key = node_dict[prev_key][0]
+            while post_key not in visited and post_key in node_dict:
+                visited.add(post_key)
+                post_key = node_dict[post_key][1]
+            curr_length = post_key - prev_key + 1
+            max_length = max(max_length, curr_length)
+
+        return max_length
+
+
+class _LeetCodeTestCases(TestCase):
+    def test_1(self):
+        nums = [100, 4, 200, 1, 3, 2]
+        output = 4
+        self.assertEqual(Solution.longestConsecutive(Solution(), nums), output)
+
+    def test_2(self):
+        nums = [0, 3, 7, 2, 5, 8, 4, 6, 0, 1]
+        output = 9
+        self.assertEqual(Solution.longestConsecutive(Solution(), nums), output)
+
+
+if __name__ == '__main__':
+    main()

maximum-subarray/EGON.py

@@ -0,0 +1,67 @@
+from typing import List
+from unittest import TestCase, main
+
+
+class Solution:
+    def maxProduct(self, nums: List[int]) -> int:
+        return self.solveWithDP(nums)
+
+    """
+    Runtime: 71 ms (Beats 61.13%)
+    Time Complexity: O(n)
+        - dp 배열 초기화를 위한 nums.copy()에 O(n)
+        - range(1, L) 조회하며 조건에 따라 연산에 O(n - 1)
+        - range(L) 조회하며 max 계산에 O(n)
+        > O(n) + O(n - 1) + O(n) ~= O(n)
+
+    Memory: 17.75 MB (Beats 11.09%)
+    Space Complexity: O(n)
+        - 크기가 n인 배열 2개 사용했으므로 2 * O(n)
+        > O(2n) ~= O(n)
+    """
+    def solveWithDP(self, nums: List[int]) -> int:
+        L = len(nums)
+        forward_product, backward_product = nums.copy(), nums.copy()
+        for i in range(1, L):
+            if forward_product[i - 1] != 0:
+                forward_product[i] *= forward_product[i - 1]
+
+            if backward_product[L - i] != 0:
+                backward_product[L - i - 1] *= backward_product[L - i]
+
+        result = nums[0]
+        for i in range(L):
+            result = max(result, forward_product[i], backward_product[i])
+
+        return result
+
+
+class _LeetCodeTestCases(TestCase):
+    def test_1(self):
+        nums = [2,3,-2,4]
+        output = 6
+        self.assertEqual(Solution.maxProduct(Solution(), nums), output)
+
+    def test_2(self):
+        nums = [-2,0,-1]
+        output = 0
+        self.assertEqual(Solution.maxProduct(Solution(), nums), output)
+
+    def test_3(self):
+        nums = [-2]
+        output = -2
+        self.assertEqual(Solution.maxProduct(Solution(), nums), output)
+
+    def test_4(self):
+        nums = [0,-3,-2,-3,-2,2,-3,0,1,-1]
+        output = 72
+        self.assertEqual(Solution.maxProduct(Solution(), nums), output)
+
+    def test_5(self):
+        nums = [7, -2, -4]
+        output = 56
+        self.assertEqual(Solution.maxProduct(Solution(), nums), output)
+
+
+if __name__ == '__main__':
+    main()

missing-number/EGON.py

@@ -0,0 +1,48 @@
+from typing import List
+from unittest import TestCase, main
+
+
+class Solution:
+    def missingNumber(self, nums: List[int]) -> int:
+        return self.solveWithSet(nums)
+
+    """
+    Runtime: 118 ms (Beats 31.19%)
+    Time Complexity:
+        - 크기가 n + 1인 List를 set로 변환에 O(n + 1)
+        - nums 배열 조회하며 set.remove에 O(n) * O(1) ~= O(n)
+        - 마지막 set에서 pop하는데 O(1)
+        > O(n + 1) + O(n) + O(1) ~= O(n)
+
+    Memory: 18.56 MB (Beats 5.%)
+    Space Complexity:
+        - 크기가 n + 1인 set 사용에 O(n + 1)
+        > O(n + 1) ~= O(n)
+    """
+    def solveWithSet(self, nums: List[int]) -> int:
+        range_set = set(range(0, len(nums) + 1))
+        for num in nums:
+            range_set.remove(num)
+
+        return range_set.pop()
+
+
+class _LeetCodeTestCases(TestCase):
+    def test_1(self):
+        nums = [3, 0, 1]
+        output = 2
+        self.assertEqual(Solution.missingNumber(Solution(), nums), output)
+
+    def test_2(self):
+        nums = [0, 1]
+        output = 2
+        self.assertEqual(Solution.missingNumber(Solution(), nums), output)
+
+    def test_3(self):
+        nums = [9, 6, 4, 2, 3, 5, 7, 0, 1]
+        output = 8
+        self.assertEqual(Solution.missingNumber(Solution(), nums), output)
+
+
+if __name__ == '__main__':
+    main()

valid-palindrome/EGON.py

@@ -0,0 +1,52 @@
+from unittest import TestCase, main
+
+
+class Solution:
+    def isPalindrome(self, s: str) -> bool:
+        return self.solveWithTwoPointer(s)
+
+    """
+    Runtime: 43 ms (Beats 68.60%)
+    Time Complexity: O(n)
+        - s 문자열 iterable 조회하며 연산에 O(n)
+        - range(0, length // 2) 조회에 O(n // 2)
+        > O(n) + O(n // 2) ~= O(n)
+
+    Memory: 17.02 MB (Beats 54.30%)
+    Space Complexity: O(n)
+        - 최대 크기가 n인 trimmed_s 변수 할당에 O(n)
+        > O(n)
+    """
+    def solveWithPointer(self, s: str) -> bool:
+        trimmed_s = ""
+        for char in s:
+            if char.isalpha() or char.isnumeric():
+                trimmed_s += char.lower()
+
+        length = len(trimmed_s)
+        for i in range(0, length // 2):
+            if trimmed_s[i] != trimmed_s[length - i - 1]:
+                return False
+        else:
+            return True
+
+
+class _LeetCodeTestCases(TestCase):
+    def test_1(self):
+        s = "A man, a plan, a canal: Panama"
+        output = True
+        self.assertEqual(Solution.isPalindrome(Solution(), s), output)
+
+    def test_2(self):
+        s = "race a car"
+        output = False
+        self.assertEqual(Solution.isPalindrome(Solution(), s), output)
+
+    def test_3(self):
+        s = " "
+        output = True
+        self.assertEqual(Solution.isPalindrome(Solution(), s), output)
+
+
+if __name__ == '__main__':
+    main()

word-search/EGON.py

@@ -0,0 +1,80 @@
+from typing import List
+from unittest import TestCase, main
+
+
+class Solution:
+    def exist(self, board: List[List[str]], word: str) -> bool:
+        return self.solveWithDFS(board, word)
+
+    """
+    Runtime: 5005 ms (Beats 27.48%)
+    Time Complexity: O((MAX_R ** 2) * (MAX_C ** 2)), upper bound
+        - 이중 for문 조회에 O(MAX_R * MAX_C)
+        - node 하나당 조회하는 DIRS의 크기가 4이고, 최대 word의 길이만큼 반복하므로 O(4 * L)
+            - 단 early return하므로 이는 upper bound
+        > O(MAX_R * MAX_C) * O(4L) ~= O(MAX_R * MAX_C * L)
+
+    Memory: 16.59 MB (Beats 69.71%)
+    Space Complexity:
+        - MAX_R * MAX_C 격자의 칸마다 stack이 생성될 수 있으므로 O(MAX_R * MAX_C)
+        - node의 크기는 visited에 지배적이고(curr_word 무시 가정), visited의 크기는 최대 L
+        > O(MAX_R * MAX_C) * O(L) ~= O(MAX_R * MAX_C * L)
+    """
+    def solveWithDFS(self, board: List[List[str]], word: str) -> bool:
+        MAX_R, MAX_C, MAX_IDX = len(board), len(board[0]), len(word)
+        DIRS = ((-1, 0), (1, 0), (0, -1), (0, 1))
+
+        for r in range(MAX_R):
+            for c in range(MAX_C):
+                if board[r][c] == word[0]:
+                    stack = [(r, c, 0, board[r][c], set([(r, c)]))]
+                    while stack:
+                        curr_r, curr_c, curr_idx, curr_word, curr_visited = stack.pop()
+
+                        if curr_word == word:
+                            return True
+
+                        for dir_r, dir_c in DIRS:
+                            post_r, post_c, post_idx = curr_r + dir_r, curr_c + dir_c, curr_idx + 1
+                            if (post_r, post_c) in curr_visited:
+                                continue
+                            if not (0 <= post_r < MAX_R and 0 <= post_c < MAX_C):
+                                continue
+                            if not (post_idx < MAX_IDX and board[post_r][post_c] == word[post_idx]):
+                                continue
+
+                            post_visited = curr_visited.copy()
+                            post_visited.add((post_r, post_c))
+                            stack.append((post_r, post_c, post_idx, curr_word + word[post_idx], post_visited))
+
+        return False
+
+
+class _LeetCodeTestCases(TestCase):
+    def test_1(self):
+        board = [["A", "B", "C", "E"], ["S", "F", "C", "S"], ["A", "D", "E", "E"]]
+        word = "ABCCED"
+        output = True
+        self.assertEqual(Solution.exist(Solution(), board, word), output)
+
+    def test_2(self):
+        board = [["A", "B", "C", "E"], ["S", "F", "C", "S"], ["A", "D", "E", "E"]]
+        word = "SEE"
+        output = True
+        self.assertEqual(Solution.exist(Solution(), board, word), output)
+
+    def test_3(self):
+        board = [["A", "B", "C", "E"], ["S", "F", "C", "S"], ["A", "D", "E", "E"]]
+        word = "ABCB"
+        output = False
+        self.assertEqual(Solution.exist(Solution(), board, word), output)
+
+    def test_4(self):
+        board = [["A","B","C","E"],["S","F","E","S"],["A","D","E","E"]]
+        word = "ABCESEEEFS"
+        output = True
+        self.assertEqual(Solution.exist(Solution(), board, word), output)
+
+
+if __name__ == '__main__':
+    main()