[BEMELON] Week 4

missing-number/bemelon.py

@@ -0,0 +1,12 @@
+class Solution:
+    # Time complexity: O(n)
+    # Space complexity: O(1)
+    def missingNumber(self, nums: List[int]) -> int:
+        visited = 0 
+        for num in nums:
+            visited |= (1 << num)
+
+        for i in range(len(nums) + 1):
+            if (not visited & (1 << i)):
+                return i
+        return -1

valid-palindrome/bemelon.py

@@ -0,0 +1,18 @@
+class Solution:
+    def isAlphaNum(self, c : str):
+        return 'a' <= c.lower() <= 'z' or '0' <= c <= '9'
+
+    # Time complexity: O(n)
+    # Space complexity: O(1)
+    def isPalindrome(self, s: str) -> bool:
+        left, right = 0, len(s) - 1
+
+        while left < right: 
+            if self.isAlphaNum(s[left]) and self.isAlphaNum(s[right]):
+                if s[left].lower() != s[right].lower():
+                    return False 
+                left, right = left + 1, right - 1
+            else:
+                left, right = left + (not self.isAlphaNum(s[left])), right - (not self.isAlphaNum(s[right]))
+
+        return True