LeetCode Online Judge 题目C# 练习 - Multiply Strings

Given two numbers represented as strings, return multiplication of the numbers as a string.
Note: The numbers can be arbitrarily large and are non-negative.

 1         public static string MultiplyStrings(string num1, string num2)
 2         {
 3             if (num1.Length == 0 || num2.Length == 0)
 4                 return "0";
 5 
 6             int carry = 0;
 7             List<int> l1 = new List<int>();
 8             List<int> l2 = new List<int>();
 9             for (int i = num2.Length - 1; i >= 0; i--)
10             {
11                 List<int> curr;
12                 if (l1.Count == 0)
13                     curr = l1;
14                 else
15                 {
16                     curr = l2;
17                     //Adding 0 to the end
18                     for (int k = i; k < num2.Length - 1; k++)
19                     {
20                         curr.Add(0);
21                     }
22                 }
23 
24                 for (int j = num1.Length - 1; j >= 0; j--)
25                 {
26                     int b = num2[i] - '0';
27                     int a = num1[j] - '0';
28                                         
29                     curr.Add(((a * b) % 10 + carry) % 10);
30                     carry = (a * b + carry) / 10;
31                 }
32 
33                 if (carry > 0)
34                     curr.Add(carry);
35 
36                 carry = 0;
37 
38                 //Adding l1 and l2 into l1;
39                 if (l2.Count > 0)
40                 {
41                     int k = 0;
42                     while (k < l1.Count || k < l2.Count)
43                     {
44                         int a = k < l1.Count ? l1[k] : 0;
45                         int b = k < l2.Count ? l2[k] : 0;
46 
47                         if (k < l1.Count)
48                             l1[k] = ((a + b + carry) % 10);
49                         else
50                             l1.Add((a + b + carry) % 10);
51                         carry = (a + b + carry) / 10;
52 
53                         k++;
54                     }
55 
56                     if (carry > 0)
57                         l1.Add(carry);
58 
59                     carry = 0;
60                 }
61                 l2.Clear();
62             }
63 
64             string ret = "";
65             for (int i = l1.Count - 1; i >= 0; i--)
66             {
67                 if (l1[i] != 0 || ret != "")
68                     ret = ret + l1[i].ToString();
69             }
70 
71             return ret == "" ? "0" : ret; ;
72         }

代码分析：

　　也是没有技巧的题目，细心注意输出的结果就行。

posted @ 2012-10-01 22:36  ETCOW  阅读(285)  评论(0)  编辑  收藏  举报