题解 | #比较版本号#

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 比较版本号
     * @param version1 string字符串 
     * @param version2 string字符串 
     * @return int整型
     */
    public int compare (String version1, String version2) {
        // write code here
        if (version1 == null && version2 == null) {
            return 0;
        } else if (version2 == null && version2 != null) {
            return -1;
        } else if (version1 != null && version2 == null) {
            return 1;
        } else if (version1.equals(version2)) {
            return 0;
        }
        
        String[] part1 = version1.split("\\.");
        String[] part2 = version2.split("\\.");
        
        int i = 0, j = 0;
        int max = Math.max(part1.length, part2.length);
        for (int k = 0; k < max; k++) {
            String str1 = i < part1.length ? part1[i++] : "0";
            String str2 = j < part2.length ? part2[j++] : "0";
            
            int diff = Math.abs(str1.length() - str2.length());
            if (str1.length() < str2.length()) {
                str1 = getZero(diff) + str1;
            } else if (str1.length() > str2.length()) {
                str2 = getZero(diff) + str2;
            }
            
            int res = str1.compareTo(str2);
            if (res != 0) {
                return res > 0 ? 1 : -1;
            }
        }
        return 0;
    }
    
    private String getZero(int n) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < n; i++) {
            sb.append("0");
        }
        return sb.toString();
    }
}