basic addition

Author: Arjiit

Two Pointers/addBinary.java

@@ -0,0 +1,36 @@
+class Solution {
+    public String addBinary(String a, String b) {
+        /*
+        Starting from the last bit, snd appending the result to string and noting the carry
+        */
+        StringBuilder sb = new StringBuilder();
+        int i = a.length() - 1;
+        int j = b.length() - 1;
+        int carry = 0;
+        
+        while(i>=0 || j>= 0) {
+            int sum = carry;
+            if (j>=0) {
+                sum = sum + b.charAt(j) - '0'; // '1' - '0' = 1
+             //   System.out.println(sum);
+                j--;
+            }
+            
+            if (i >= 0) {
+                sum = sum + a.charAt(i) - '0';
+              //  System.out.println(sum);
+                i--;
+            }
+            sb.append(sum % 2);
+            
+            carry = sum/2;
+            // System.out.println("carry " + carry);
+        }
+        
+        if (carry != 0) {
+            sb.append(carry);
+        }
+        
+        return sb.reverse().toString();
+    }
+}