[sun]Week4 문제풀이

longest-consecutive-sequence/sun912.py

@@ -0,0 +1,19 @@
+"""
+TC: O(n)
+SC: O(n)
+"""
+
+class Solution:
+    def longestConsecutive(self, nums: List[int]) -> int:
+        longest = 0
+        num_set = set(nums)
+        print(num_set)
+
+        for n in num_set:
+            if (n-1) not in num_set:
+                length = 1
+                while (n+length) in num_set:
+                    length += 1
+                longest = max(longest, length)
+
+        return longest

maximum-product-subarray/sun912.py

@@ -0,0 +1,15 @@
+"""
+    TC: O(n)
+    SC: O(1)
+"""
+class Solution:
+    def maxProduct(self, nums: List[int]) -> int:
+        minimum, maximum = 1, 1
+        result = nums[0]
+
+        for num in nums:
+            minimum, maximum = min(minimum * num, maximum * num, num), max(minimum * num, maximum * num, num)
+            result = max(maximum, result)
+
+        return result
+

missing-number/sun912.py

@@ -0,0 +1,12 @@
+"""
+TC: O(n)
+SC: O(n)
+"""
+
+class Solution:
+    def missingNumber(self, nums: List[int]) -> int:
+        nums_set = set(nums)
+        for i in range(len(nums)):
+            if i not in nums_set:
+                return i
+        return len(nums)

valid-palindrome/sun912.py

@@ -0,0 +1,22 @@
+"""
+TC: O(n)
+SC: O(n)
+"""
+class Solution:
+    def isPalindrome(self, s: str) -> bool:
+        str = list(s.lower())
+        chars = []
+        for c in str:
+            if (ord(c) >= ord("a") and ord(c) <= ord("z")) or (ord(c) >= ord("0") and ord(c) <= ord("9")):
+                chars.append(c)
+
+        for i in range(len(chars)//2):
+
+            if len(c)%2 == 0:
+                if chars[i] != chars[-(i+1)]:
+                    return False
+            else:
+                if chars[i] != chars[-(i+1)]:
+                    return False
+
+        return True

word-search/sun912.py

@@ -0,0 +1,41 @@
+"""
+TC: O(ROWS*COLS*4^word length)
+SC: O(ROWS*COLS*word length)
+"""
+
+class Solution:
+    def exist(self, board: List[List[str]], word: str) -> bool:
+        ROWS = len(board)
+        COLS = len(board[0])
+        path = set()
+
+        def dfs(r,c,i):
+            if i == len(word):
+                return True
+
+            if (r < 0 or
+                    c < 0 or
+                    r >= ROWS or
+                    c >= COLS or
+                    word[i] != board[r][c] or
+                    (r,c) in path
+            ):
+                return False
+
+            path.add((r,c))
+
+            res = (dfs(r+1, c, i+1) or
+                   dfs(r, c+1, i+1) or
+                   dfs(r-1, c, i+1) or
+                   dfs(r, c-1, i+1)
+                   )
+            path.remove((r,c))
+            return res
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                if dfs(r,c, 0): return True
+
+        return False
+
+