Leetcode#165 Compare Version Numbers

按"."分割，然后比较

需要注意的地方：

1. 多于的前缀0。例如"001"="1"

2. 多余的后缀版本号。例如"1"="1.0.0.0"

代码：

 1 int compareVersion(string version1, string version2) {
 2   int last1 = -1;
 3   int last2 = -1;
 4   int i = 0;
 5   int j = 0;
 6   int k = 0;
 7 
 8   while (i < version1.length() && j < version2.length()) {
 9     // 切割
10     while (i < version1.length() && version1[i] != '.') i++;
11     while (j < version2.length() && version2[j] != '.') j++;
12     string sub1 = last1 < 0 ? version1.substr(0, i) : version1.substr(last1 + 1, i - last1 - 1);
13     string sub2 = last2 < 0 ? version2.substr(0, j) : version2.substr(last2 + 1, j - last2 - 1);
14 
15     // 去除前缀0
16     k = 0;
17     while (k < sub1.length() - 1 && sub1[k] == '0') k++;
18     sub1 = sub1.substr(k);
19     k = 0;
20     while (k < sub2.length() - 1 && sub2[k] == '0') k++;
21     sub2 = sub2.substr(k);
22 
23     // 比较
24     if (sub1.length() == sub2.length()) {
25       for (int k = 0; k < sub1.length(); k++) {
26         if (sub1[k] == sub2[k])
27           continue;
28         return sub1[k] > sub2[k] ? 1 : -1;
29       }
30       last1 = i++;
31       last2 = j++;
32     }
33     else
34       return sub1.length() > sub2.length() ? 1 : -1;
35   }
36 
37   // 去除冗余后缀版本号
38   while (i < version1.length() && (version1[i] == '0' || version1[i] == '.'))
39     i++;
40   while (j < version2.length() && (version2[j] == '0' || version2[j] == '.'))
41     j++;
42 
43   if (i < version1.length())
44     return 1;
45   if (j < version2.length())
46     return -1;
47   return 0;
48 }