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leetcode - Multiply Strings

2013-12-10 18:19  张汉生  阅读(137)  评论(0)    收藏  举报

 

 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 };