If version1 > version2 return 1, if version1 < version2 return -1, otherwise return 0.
You may assume that the version strings are non-empty and contain only digits and the . character.
The . character does not represent a decimal point and is used to separate number sequences.
For instance, 2.5 is not "two and a half" or "half way to version three", it is the fifth second-level revision of the second first-level revision.
Here is an example of version numbers ordering:
[分析] 两种方法的主要思路是一致的,比较点号分割出来的每一个子串对应的数字。两个版本串的点号可能不一样多,为了正确比较诸如(1.0, 1) 或者(1.0.1, 1)这样的情况,实现时点号少的串可以视为后面都是0,一直比较到长串结束。Method1 需要额外空间,且注意String的split方法不能使用点号进行分割。Method2 不需要额外空间。
// Method 1 public int compareVersion(String version1, String version2) { if (version1 != null && version2 != null) { version1 = version1.replace('.', ':'); version2 = version2.replace('.', ':'); String[] num1 = version1.split(":"); String[] num2 = version2.split(":"); int val1 = 0; int val2 = 0; int i = 0; while (i < num1.length || i < num2.length) { val1 = 0; val2 = 0; if (i < num1.length) val1 = Integer.parseInt(num1[i]); if (i < num2.length) val2 = Integer.parseInt(num2[i]); if (val1 < val2) return -1; else if (val1 > val2) return 1; i++; } return 0; } else if (version1 != null) { return 1; } else if (version2 != null) { return -1; } else { return 0; } } // Method 2 public int compareVersion(String version1, String version2) { if (version1 != null && version2 != null) { int p1 = 0, p2 = 0; int nextDot1 = -1, nextDot2 = -1; int n1 = version1.length(), n2 = version2.length(); int sub1 = 0, sub2 = 0; while (p1 < n1 || p2 < n2) { nextDot1 = version1.indexOf('.', p1); nextDot2 = version2.indexOf('.', p2); if (p1 < n1) sub1 = Integer.valueOf(version1.substring(p1, nextDot1 != -1 ? nextDot1 : n1)); else sub1 = 0; if (p2 < n2) sub2 = Integer.valueOf(version2.substring(p2, nextDot2 != -1 ? nextDot2 : n2)); else sub2 = 0; if (sub1 > sub2) return 1; else if (sub1 < sub2) return -1; p1 = nextDot1 != -1 ? (nextDot1 + 1) : n1; p2 = nextDot2 != -1 ? (nextDot2 + 1) : n2; } return 0; } else if (version1 == null) { return -1; } else if (version2 == null) { return 1; } else { return 0; } }