bitwise op

Divide Two Integers.py

@@ -0,0 +1,53 @@
+"""
+Divide two integers without using multiplication, division and mod operator.
+
+If it is overflow, return 2147483647
+
+Example
+Given dividend = 100 and divisor = 9, return 11.
+"""
+__author__ = 'Daniel'
+
+
+class Solution:
+    def divide(self, dividend, divisor):
+        q = 0
+        if dividend == 0 or divisor == 0:
+            return 0
+
+        # pitfall, overflow
+        MAXINT = 2147483647
+        MININT = -2147483648
+        if dividend == MININT and divisor == -1:
+            return MAXINT
+
+        sign = 1 if dividend*divisor > 0 else -1
+        dividend, divisor = abs(dividend), abs(divisor)
+
+        d = divisor
+        q_cur = 1
+        if divisor > dividend:
+            return 0
+
+        while d<<1 < dividend:
+            d <<= 1
+            q_cur <<= 1
+
+        q += q_cur
+        dividend -= d
+
+        while dividend:
+            if divisor > dividend:
+                break
+
+            while d > dividend:
+                d >>= 1
+                q_cur >>= 1
+
+            q += q_cur
+            dividend -= d
+
+        return q*sign
+
+if __name__ == "__main__":
+    print Solution().divide(-1, 1)