题解 | #比较版本号#

import java.util.*;


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) {
        int index1 = 0,index2 = 0;
        String[] arr1 = splitByDigit(version1);
        String[] arr2 = splitByDigit(version2);
        while(index1 < arr1.length && index2 < arr2.length){
            if(parseInt(arr1[index1].toCharArray()) < parseInt(arr2[index2].toCharArray())){
                return -1;
            }else if(parseInt(arr1[index1].toCharArray()) > parseInt(arr2[index2].toCharArray())){
                return 1;
            }else {
                index1++;
                index2++;
            }  
        }
        while(index1 < arr1.length){
            if(parseInt(arr1[index1].toCharArray()) != 0){
                return 1;
            }
            index1 ++;
        }
        
        while(index2 < arr2.length){
            if(parseInt(arr2[index2].toCharArray()) != 0){
                return 1;
            }
            index2 ++;
        }
        return 0;
        
    }
    
    private String[] splitByDigit(String s){
        int begin = -1,rush = 0;
        char[] arr = s.toCharArray();
        List<String> list = new ArrayList<>();
        while(rush < arr.length){
        	begin = rush;
            while(rush < arr.length && arr[rush] != '.') {
            	rush++;
            }
            list.add(new String(arr,begin,rush - begin));
            ++rush;
        }
        return list.toArray(new String[0]);
    }
    
    private int parseInt(char[] arr){
        int i = 0;
        // 跳过前导 0
        while(arr[i] == 0) {
        	i++;
        }
        int ret = 0;
        while(i < arr.length){
            ret += ret * 10 + (arr[i++] - '0');
        }
        return ret;
    }
}