1017 Convert to Base -2.py

Author: rajeevranjancom

1017 Convert to Base -2.py

@@ -0,0 +1,67 @@
+#!/usr/bin/python3
+"""
+Given a number N, return a string consisting of "0"s and "1"s that represents
+its value in base -2 (negative two).
+
+The returned string must have no leading zeroes, unless the string is "0".
+
+
+
+Example 1:
+
+Input: 2
+Output: "110"
+Explantion: (-2) ^ 2 + (-2) ^ 1 = 2
+Example 2:
+
+Input: 3
+Output: "111"
+Explantion: (-2) ^ 2 + (-2) ^ 1 + (-2) ^ 0 = 3
+Example 3:
+
+Input: 4
+Output: "100"
+Explantion: (-2) ^ 2 = 4
+
+
+Note:
+0 <= N <= 10^9
+"""
+from collections import deque
+
+
+class Solution:
+    def baseNeg2(self, N: int) -> str:
+        """
+        % -2, // -2 ? not really
+
+        alternating
+
+
+        3
+        (-2) ^ 2 + (-2) ^ 1 + (-2) ^ 0, LSB set
+        minus reminder, divide by -2
+        (-2) ^ 1 + (-2) ^ 0, LSB set
+        minus reminder, divide by -2
+        (-2) ^ 0, LSB set
+
+        4
+        (-2) ^ 2 + 0 ^ 1 + 0 ^ 0, LSB not set
+        minus reminder, divide by -2
+        (-2) ^ 1 + 0 ^ 0, LSB not set
+        minus reminder, divide by -2
+        (-2) ^ 0, LSB set
+        """
+        ret = deque()
+        while N != 0:
+            r = N % 2  # r is the range of 0 and 2
+            ret.appendleft(r)
+            N -= r
+            N //= -2
+
+        return "".join(map(str, ret)) or "0"
+
+
+if __name__ == "__main__":
+    assert Solution().baseNeg2(3) == "111"
+    assert Solution().baseNeg2(4) == "100"