LeetCode算法题解-第七道题
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Hi! 
LeetCode 第七道题: Reverse Integer，难度简单。
Given a 32-bit signed integer, reverse digits of an integer.
Example 1:
Input: 123 Output: 321 Example 2:
Input: -123 Output: -321 Example 3:
Input: 120 Output: 21 Note: Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231, 231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.
最近一周家里有急事，先写了一个解法，后面优化。
1 public class Solution {
2 public int Reverse(int x)
3 {
4
5 int flag = 1;
6 if (x < 0)
7 {
8 flag = -1;
9 x = -1 * x;
10 }
11
12 var str = x.ToString();
13 var strL = "";
14 var strR = "";
15 var len = str.Length;
16 for (int i = 0; i < len; i++)
17 {
18 if (i < len - i - 1)
19 {
20 if (!string.IsNullOrEmpty(strL) || str[len - i - 1] != '0')
21 {
22 strL += str[len - i - 1].ToString();
23 }
24
25 strR = str[i].ToString() + strR;
26 }
27 else if (i == len - i - 1)
28 {
29 strL += str[i];
30 break;
31 }
32 else
33 {
34 break;
35 }
36 }
37
38 str = strL + strR;
39
40 var min = -1 * Math.Pow(2, 31);
41 var max = Math.Pow(2, 31) - 1;
42
43 double num = 0;
44 for (var i = 0; i < str.Length; i++)
45 {
46 num += int.Parse(str[i].ToString()) * Math.Pow(10, str.Length - i - 1);
47 var signNum = flag * num;
48 if (signNum> max || signNum < min)
49 {
50 return 0;
51 }
52 }
53
54 return flag * int.Parse(num.ToString());
55 }
56 }Gist code
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