add cpp solution

Author: jinshendan

July-LeetCoding-Challenge/19-Add-Binary/Add-Binary.cpp

@@ -0,0 +1,15 @@
+class Solution {
+public:
+    string addBinary(string a, string b) {
+        string ans = (a.length() > b.length())?a:b;
+        int sum = 0;
+        for (int i = 0; i < ans.length(); i++){
+            if (i < a.length()) sum += (a[a.length() - i - 1] == '1')?1:0;
+            if (i < b.length()) sum += (b[b.length() - i - 1] == '1')?1:0;
+            ans[ans.length() - i - 1] = (sum & 1) + '0';
+            sum >>= 1;
+        }
+        if (sum == 1) ans = "1" + ans;
+        return ans;
+    }
+};