another implementation

Author: haoel

algorithms/cpp/multiplyStrings/multiplyStrings.cpp

@@ -71,6 +71,69 @@ string multiply(string num1, string num2) {
 }
 
 
+/********************************************************************************** 
+ *                            Another implementation
+ **********************************************************************************/
+
+class Solution {
+    public:
+
+        string strPlus(string& num1, string& num2) {
+            if (num1.size()==0) return num2;
+            if (num2.size()==0) return num1;
+
+            if ( num1.size() < num2.size() ) {
+                swap(num1, num2);
+            }
+
+            string s;
+            int carry=0;
+            int x;
+            for (int i=num1.size()-1, j=num2.size()-1; i>=0; i--, j--) {
+                x = num1[i]-'0' + carry;
+                if(j>=0){
+                    x += num2[j]-'0';
+                }
+                s.insert(s.begin(), x%10+'0');
+                carry = x/10;
+            }
+            if (carry>0) {
+                s.insert(s.begin(), carry+'0');
+            }
+
+            return s;
+        }
+
+
+        string multiply(string num1, string num2) {
+
+            if (num1.size()<=0 || num2.size()<=0) return "";
+
+            string result;
+            for ( int i=num1.size()-1; i>=0; i--) {
+                int carry = 0;
+                string val;
+                for( int j=num2.size()-1; j>=0; j--) {
+                    int v = (num2[j]-'0') * (num1[i]-'0') + carry;
+                    val.insert(val.begin(), v%10+'0');
+                    carry = v/10;
+                }
+                if (carry) val.insert(val.begin(), carry+'0');
+                for (unsigned int j=i; j<num1.size()-1; j++) {
+                    val.push_back('0');
+                }
+                result = strPlus(result, val);
+            }
+
+            //check if it is zero
+            if (result[0]=='0') return "0";
+            return result;
+
+        }
+};
+
+
+
 int main(int argc, char**argv)
 {
     string s1="20";