题解 | #数字字符串转化成IP地址#

using System;
using System.Collections.Generic;


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
     *
     * 
     * @param s string字符串 
     * @return string字符串一维数组
     */
    public List<string> restoreIpAddresses (string s) {
        List<string> res = new List<string>();
        if(s.Length > 12) return res;
        if(s.Length < 4) return res;
        for(int i = 1; i < 5; i++){
            for(int j = 1; j < 5; j++){
                for(int k = 1; k < 5; k++){
                    if(i + j + k >= s.Length) continue;
                    if(i + j + k < s.Length - 4) continue;
                    string a = s.Substring(0, i);
                    string b = s.Substring(i, j);
                    string c = s.Substring(i + j, k);
                    string d = s.Substring(i + j + k, s.Length - i - k - j);
                    if(Int32.Parse(a) > 255 || Int32.Parse(b) > 255 || Int32.Parse(c) > 255 || Int32.Parse(d) > 255) continue;
                    if((a.Length != 1 && a[0] == '0') || (b.Length != 1 && b[0] == '0') || (c.Length != 1 && c[0] == '0') || (d.Length != 1 && d[0] == '0')) continue;
                    String temp = a + "." + b + "." + c + "." + d;
                    res.Add(temp);
                }
            }
        }
        return res;
    }
}