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 }