counting-bits, encode-and-decode-strings solved

Author: sun912

counting-bits/sun912.py

@@ -0,0 +1,17 @@
+"""
+
+"""
+
+
+class Solution:
+    def countBits(self, n: int) -> List[int]:
+        dp = [0] * (n+1)
+        offset = 1
+
+        for i in range(1, n+1):
+            if offset * 2 == i:
+                offset = i
+            dp[i] = 1 + dp[i-offset]
+        return dp
+
+

encode-and-decode-strings/sun912.py

@@ -0,0 +1,30 @@
+"""
+TC: O(n)
+
+"""
+class Solution:
+    """
+    @param: strs: a list of strings
+    @return: encodes a list of strings to a single string.
+    """
+    def encode(self, strs):
+        result = ""
+        for str in strs:
+            result += str(len(str)) + "#" + str
+        return result
+
+    """
+    @param: str: A string
+    @return: decodes a single string to a list of strings
+    """
+    def decode(self, str):
+        result = []
+        idx = 0
+        while idx < len(str):
+            temp_idx = idx
+            while str[temp_idx] != "#":
+                temp_idx += 1
+            length = int(str[idx:temp_idx])
+            result.append(str[temp_idx+1:temp_idx+length+1])
+            idx = temp_idx + length + 1
+        return result