@@ -183,6 +183,7 @@ My accepted leetcode solutions to some of the common interview problems.
 - [Valid Palindrome](problems/src/string/ValidPalindrome.java) (Easy)
 - [Simplify Path](problems/src/string/SimplifyPath.java) (Medium)
 - [Permutation in String](problems/src/string/PermutationInString.java) (Medium)
+- [Add Binary](problems/src/string/AddBinary.java) (Easy)
 
 #### [Tree](problems/src/tree)
 
 
@@ -0,0 +1,50 @@
+package string;
+
+/**
+ * Created by gouthamvidyapradhan on 25/11/2017.
+ *
+ * Given two binary strings, return their sum (also a binary string).
+
+ For example,
+ a = "11"
+ b = "1"
+ Return "100".
+ */
+public class AddBinary {
+
+    /**
+     * Main method
+     * @param args
+     */
+    public static void main(String[] args) {
+        System.out.println(new AddBinary().addBinary("000001010000101001", "0"));
+    }
+
+    public String addBinary(String a, String b) {
+        if(a.length() > b.length()){
+            return calculate(a, b);
+        } else return calculate(b, a);
+    }
+
+    /**
+     * Calculate sum
+     * @param a length of a should always be greater or equal to b
+     * @param b length of b should always be smaller of equal to a
+     * @return
+     */
+    private String calculate(String a, String b){
+        int carry = 0;
+        int d = a.length() - b.length();
+        StringBuilder sb = new StringBuilder();
+        for(int i = a.length() - 1; i >= 0; i --){
+            int first = Integer.parseInt(String.valueOf(a.charAt(i)));
+            int second = i - d >= 0 ? Integer.parseInt(String.valueOf(b.charAt(i - d))) : 0;
+            int sum = (first + second + carry);
+            carry = sum / 2;
+            sb.append(sum % 2);
+        }
+        if(carry != 0)
+            sb.append(carry);
+        return sb.reverse().toString();
+    }
+}