@@ -8,6 +8,7 @@ LeetCode
 
 | # | Title | Solution | Difficulty |
 |---| ----- | -------- | ---------- |
+|415|[Add Strings](https://leetcode.com/problems/add-strings/) | [C++](./algorithms/cpp/addStrings/AddStrings.cpp)|Easy|
 |406|[Queue Reconstruction by Height](https://leetcode.com/problems/queue-reconstruction-by-height/) | [C++](./algorithms/cpp/queueReconstructionByHeight/QueueReconstructionByHeight.cpp)|Medium|
 |405|[Convert a Number to Hexadecimal](https://leetcode.com/problems/convert-a-number-to-hexadecimal/) | [C++](./algorithms/cpp/convertANumberToHexadecimal/ConvertANumberToHexadecimal.cpp)|Easy|
 |404|[Sum of Left Leaves](https://leetcode.com/problems/sum-of-left-leaves/) | [C++](./algorithms/cpp/sumOfLeftLeaves/SumOfLeftLeaves.cpp)|Easy|
 
@@ -0,0 +1,48 @@
+// Source : https://leetcode.com/problems/add-strings/
+// Author : Hao Chen
+// Date   : 2016-11-12
+
+/*************************************************************************************** 
+ *
+ * Given two non-negative numbers num1 and num2 represented as string, return the sum 
+ * of num1 and num2.
+ * 
+ * Note:
+ * 
+ * The length of both num1 and num2 is 
+ * Both num1 and num2 contains only digits 0-9.
+ * Both num1 and num2 does not contain any leading zero.
+ * You must not use any built-in BigInteger library or convert the inputs to integer 
+ * directly.
+ ***************************************************************************************/
+
+class Solution {
+public:
+    string addStrings(string num1, string num2) {
+        string& longstr  = ( num1.size() >= num2.size() ? num1 : num2 );
+        string& shortstr = ( num1.size() <  num2.size() ? num1 : num2 );
+        
+        int longlen = longstr.size();
+        int shortlen = shortstr.size();
+        
+        char carry = 0;
+        int i, j;
+        
+        string result;
+        for (i = longlen-1, j=shortlen-1; i>=0; i--, j--) {
+            int add = 0;
+            if (j>=0) {
+                add = longstr[i] + shortstr[j] - 2 * '0' + carry;
+            }else{
+                add = longstr[i] - '0' + carry;
+            }
+            carry = add/10;
+            result = char('0' + add % 10) + result;
+        }
+        
+        if (carry) {
+            result = '1' + result;
+        }
+        return result;
+    }
+};