2

Author: kedebug

MultiplyStrings/MultiplyStrings.cpp

@@ -0,0 +1,40 @@
+class Solution {
+public:
+    string multiply(string num1, string num2) {
+        // Start typing your C/C++ solution below
+        // DO NOT write int main() function
+        
+        int len_num1 = num1.size();
+        int len_num2 = num2.size();
+        
+        vector<int> multiply_num(len_num1 + len_num2, 0);
+        
+        for (int i = len_num1 - 1; i >= 0; i--) {
+            for (int j = len_num2 - 1; j >= 0; j--) {
+                int a = num1[i] - '0';
+                int pa = len_num1 - i - 1;
+                int b = num2[j] - '0';
+                int pb = len_num2 - j - 1;
+                multiply_num[pa + pb] += a * b;
+            }
+        }
+        for (int i = 0; i < multiply_num.size(); i++) {
+            if (multiply_num[i] > 0) {
+                multiply_num[i+1] += multiply_num[i] / 10;
+                multiply_num[i] = multiply_num[i] % 10;
+            }
+        }
+        
+        while (multiply_num[multiply_num.size()-1] == 0)
+            multiply_num.pop_back();
+        
+        string num;
+        for (auto iter = multiply_num.rbegin(); iter != multiply_num.rend(); iter++)
+            num += (char)(*iter + '0');
+        
+        if (num.empty())
+            num = "0";
+        
+        return num;
+    }
+};