Update add-binary.cpp

kamyu104 · kamyu104 · commit 9c38ca4d0ca9 · 2016-02-19T21:32:17.000+08:00
diff --git a/C++/add-binary.cpp b/C++/add-binary.cpp
@@ -4,23 +4,53 @@
 class Solution {
 public:
     string addBinary(string a, string b) {
-        string result;
-        int result_length = max(a.length(), b.length()) ;
+        string res;
+        size_t res_len = max(a.length(), b.length()) ;
 
-        int carry = 0;
-        for (int i = 0; i < result_length; ++i) {
-            int a_bit_i = i < a.length() ? a[a.length() - 1 - i] - '0' : 0;
-            int b_bit_i = i < b.length() ? b[b.length() - 1 - i] - '0' : 0;
-            int sum = carry + a_bit_i + b_bit_i;
+        size_t carry = 0;
+        for (int i = 0; i < res_len; ++i) {
+            const size_t a_bit_i = i < a.length() ? a[a.length() - 1 - i] - '0' : 0;
+            const size_t b_bit_i = i < b.length() ? b[b.length() - 1 - i] - '0' : 0;
+            size_t sum = carry + a_bit_i + b_bit_i;
             carry = sum / 2;
             sum %= 2;
-            result.push_back('0' + sum);
+            res.push_back('0' + sum);
         }
         if (carry) {
-            result.push_back('0' + carry);
+            res.push_back('0' + carry);
         }
-        reverse(result.begin(), result.end());
+        reverse(res.begin(), res.end());
 
-        return result;
+        return res;
+    }
+};
+
+class Solution2 {
+public:
+    string addBinary(string a, string b) {
+        size_t carry = 0;
+        string res;
+
+        for (auto a_it = a.rbegin(), b_it = b.rbegin(); a_it != a.rend() || b_it != b.rend();) {
+            const size_t a_bit_i = (a_it != a.rend()) ? *a_it - '0' : 0;
+            const size_t b_bit_i = (b_it != b.rend()) ? *b_it - '0' : 0;
+            size_t sum = a_bit_i + b_bit_i + carry;
+            carry = sum / 2;
+            sum %= 2;
+            res.push_back('0' + sum);
+
+            if (a_it != a.rend()) {
+                ++a_it;
+            }
+            if (b_it != b.rend()) {
+                ++b_it;
+            }
+        }
+        if (carry) {
+            res.push_back('0' + carry);
+        }
+        reverse(res.begin(), res.end());
+
+        return res;
     }
 };
