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165. Compare Version Numbers

Compare two version numbers version1 and version2.

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.

You may assume the default revision number for each level of a version number to be 0. For example, version number 3.4 has a revision number of 3 and 4 for its first and second level revision number. Its third and fourth level revision number are both 0.

Example 1:

Input: version1 = "0.1", version2 = "1.1"
Output: -1

Example 2:

Input: version1 = "1.0.1", version2 = "1"
Output: 1

Example 3:

Input: version1 = "7.5.2.4", version2 = "7.5.3"
Output: -1

Example 4:

Input: version1 = "1.01", version2 = "1.001"
Output: 0
Explanation: Ignoring leading zeroes, both “01” and “001" represent the same number “1”

Example 5:

Input: version1 = "1.0", version2 = "1.0.0"
Output: 0
Explanation: The first version number does not have a third level revision number, which means its third level revision number is default to "0"

Note:

Version strings are composed of numeric strings separated by dots . and this numeric strings may have leading zeroes.
Version strings do not start or end with dots, and they will not be two consecutive dots.

难度：medium

题目：比较两个版本version1和version2.

如果1大于2返回1,1小于2返回－1，否则返回0.假定版本字符串中非空且只含有数字和点。点不是小数点只是用作分隔符。

思路：按点号分割转成数字比较。

Runtime: 1 ms, faster than 89.87% of Java online submissions for Compare Version Numbers.

Memory Usage: 33.1 MB, less than 100.00% of Java online submissions for Compare Version Numbers.

class Solution {
    public int compareVersion(String version1, String version2) {
        String[] vs1 = version1.split("//.");
        String[] vs2 = version2.split("//.");
        for (int i = 0; i < Math.max(vs1.length, vs2.length); i++) {
            int i1 = i < vs1.length ? Integer.parseInt(vs1[i]) : 0;
            int i2 = i < vs2.length ? Integer.parseInt(vs2[i]) : 0;
            if (i1 - i2 > 0) {
                return 1;
            } 
            if (i1 - i2 < 0) {
                return -1;
            }
        }
        
        return 0;
    }
}

原文 https://segmentfault.com/a/1190000018147989

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