Saysimple week4

counting-bits/saysimple.py

@@ -0,0 +1,11 @@
+# TC: O(n), SC: O(n)
+
+class Solution:
+    def countBits(self, n: int) -> List[int]:
+        answer = []
+
+        for i in range(n+1):
+            b = bin(i)
+            answer.append(int(b.count("1")))
+
+        return answer

group-anagrams/saysimple.py

@@ -0,0 +1,14 @@
+# TC: O(n), SC: O(n)
+
+from collections import defaultdict
+
+class Solution:
+    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
+        d = defaultdict(list)
+        for s in strs:
+            if not s:
+                d["0"].append("")
+            else:
+                d["".join(sorted(s))].append(s)
+
+        return [d[s] for s in d]

missing-number/saysimple.py

@@ -0,0 +1,7 @@
+# TC: O(n), SC: O(1)
+
+class Solution:
+    def missingNumber(self, nums: List[int]) -> int:
+        for i in range(len(nums)+1):
+            if i not in nums:
+                return i

number-of-1-bits/saysimple.py

@@ -0,0 +1,5 @@
+# TC: O(1), SC: O(1)
+
+class Solution:
+    def hammingWeight(self, n: int) -> int:
+        return bin(n).count("1")

reverse-bits/saysimple.py

@@ -0,0 +1,5 @@
+# TC: O(1), SC: O(1)
+
+class Solution:
+    def reverseBits(self, n: int) -> int:
+        return int(f"{bin(n)[2:]:0>32}"[::-1], 2)