[mangodm-web] Week 02 Solutions

construct-binary-tree-from-preorder-and-inorder-traversal/mangodm-web.py

@@ -0,0 +1,32 @@
+from typing import List
+
+
+class Codec:
+    def encode(self, strs: List[str]) -> str:
+        """Encodes a list of strings to a single string."""
+        encoded = []
+
+        for s in strs:
+            encoded.append(s.replace("/", "//") + "/:")
+
+        return "".join(encoded)
+
+    def decode(self, s: str) -> List[str]:
+        """Decodes a single string to a list of strings."""
+        decoded = []
+        current_string = ""
+        i = 0
+
+        while i < len(s):
+            if s[i : i + 2] == "/:":
+                decoded.append(current_string)
+                current_string = ""
+                i += 2
+            elif s[i : i + 2] == "//":
+                current_string += "/"
+                i += 2
+            else:
+                current_string += s[i]
+                i += 1
+
+        return decoded

counting-bits/mangodm-web.py

@@ -0,0 +1,11 @@
+from typing import List
+
+
+class Solution:
+    def countBits(self, n: int) -> List[int]:
+        answer = [0]
+
+        for i in range(1, n + 1):
+            answer.append(answer[i // 2] + i % 2)
+
+        return answer

decode-ways/mangodm-web.py

@@ -0,0 +1,16 @@
+class Solution:
+    def numDecodings(self, s: str) -> int:
+        if s[0] == "0":
+            return 0
+
+        n = len(s)
+        dp = [0] * (n + 1)
+        dp[0], dp[1] = 1, 1
+
+        for i in range(2, n + 1):
+            if s[i - 1] != "0":
+                dp[i] += dp[i - 1]
+            if "10" <= s[i - 2 : i] <= "26":
+                dp[i] += dp[i - 2]
+
+        return dp[n]

encode-and-decode-strings/mangodm-web.py

@@ -0,0 +1,32 @@
+from typing import List
+
+
+class Codec:
+    def encode(self, strs: List[str]) -> str:
+        """Encodes a list of strings to a single string."""
+        encoded = []
+
+        for s in strs:
+            encoded.append(s.replace("/", "//") + "/:")
+
+        return "".join(encoded)
+
+    def decode(self, s: str) -> List[str]:
+        """Decodes a single string to a list of strings."""
+        decoded = []
+        current_string = ""
+        i = 0
+
+        while i < len(s):
+            if s[i : i + 2] == "/:":
+                decoded.append(current_string)
+                current_string = ""
+                i += 2
+            elif s[i : i + 2] == "//":
+                current_string += "/"
+                i += 2
+            else:
+                current_string += s[i]
+                i += 1
+
+        return decoded

valid-anagram/mangodm-web.py

@@ -0,0 +1,9 @@
+from collections import Counter
+
+
+class Solution:
+    def isAnagram(self, s: str, t: str) -> bool:
+        if len(s) != len(t):
+            return False
+
+        return Counter(s) == Counter(t)