1 class Solution {
2 public:
3 string multiply(string num1, string num2) {
4 // IMPORTANT: Please reset any member data you declared, as
5 // the same Solution instance will be reused for each test case.
6 int len1 = num1.length();
7 int len2 = num2.length();
8 if (len1<=0 || len2<=0)
9 return "";
10 int * a = new int[len1];
11 int * b = new int[len2];
12 for (int i=0; i<len1; i++)
13 a[len1-i-1] = num1.at(i)-'0';
14 for (int i=0; i<len2; i++)
15 b[len2-i-1] = num2.at(i)-'0';
16 int * c = new int[len1+len2];
17 for (int i=0; i<len1+len2; i++){
18 c[i] = 0;
19 }
20 for (int i=0; i<len1; i++)
21 for (int j=0; j<len2; j++)
22 c[i+j] += a[i] *b[j];
23 for (int i=0; i<len1+len2-1; i++){
24 if (c[i]>=10){
25 c[i+1] += c[i]/10;
26 c[i] %= 10;
27 }
28 }
29 string rlt = "";
30 bool flag = false;
31 for (int i=len1+len2-1; i>=0; i--){
32 if (c[i]!=0)
33 flag = true;
34 if (flag)
35 rlt += (char)('0'+c[i]);
36 }
37 delete []a;
38 delete []b;
39 delete []c;
40 if (rlt=="")
41 rlt = "0";
42 return rlt;
43 }
44 };
