Added Day-19 Solution

Author: Gangadharbhuvan

Day-19_Add_Binary.py

@@ -0,0 +1,33 @@
+'''
+	Given two binary strings, return their sum (also a binary string).
+
+The input strings are both non-empty and contains only characters 1 or 0.
+
+Example 1:
+
+Input: a = "11", b = "1"
+Output: "100"
+Example 2:
+
+Input: a = "1010", b = "1011"
+Output: "10101"
+ 
+
+Constraints:
+
+Each string consists only of '0' or '1' characters.
+1 <= a.length, b.length <= 10^4
+Each string is either "0" or doesn't contain any leading zero.
+
+'''
+
+class Solution:
+    def addBinary(self, a, b):
+        i, j, summ, carry = len(a) - 1, len(b) - 1, "", 0
+        while i >= 0 or j >= 0 or carry:
+            d1 = int(a[i]) if i >= 0 else 0
+            d2 = int(b[j]) if j >= 0 else 0
+            summ += str((d1 + d2 + carry) % 2)
+            carry = (d1 + d2 + carry) // 2
+            i, j = i-1, j-1 
+        return summ[::-1]