题解 | #合法IP#

import java.util.Arrays;
import java.util.Scanner;
public class Main {
    public static void main(String args[]) {
        Scanner scan = new Scanner(System.in);
        while (scan.hasNext()) {
            String ip = scan.nextLine();
            String [] iparray = ip.split("\\.");////\\符号
            boolean flag = true;
            boolean flag2 = false;
            if (iparray.length == 4 ) {
                for (int i = 0; i < iparray.length; i++) {
                    if (iparray[i].equals("")) {////equals中有s，字符串可用equals，char没有equals函数
                        flag = false;
                        break;
                    } else {
                        int temp = Integer.parseInt(iparray[i]);////parse语法解析的意思
                        if (temp < 0 || temp >= 256) {
                            flag = false;
                            break;
                        }
                        char [] tempc = iparray[i].toCharArray();
                        for (int j = 0; j < tempc.length; j++) {
                            String temp3 = "" + tempc[j];
                            if (temp3.equals("+")) {
                                flag = false;
                                break;
                            }
                        }
                        if (tempc.length >= 2 && !("" + tempc[0]).equals("+") &&
                                Integer.parseInt("" + tempc[0]) == 0) {
                            flag = false;
                            break;
                        }
                    }
                }
            } else {
                flag = false;
            }
            if (flag) {
                System.out.println("YES");
            } else {
                System.out.println("NO");
            }
        }
    }
}