合法IP

while True:
    try:
        # 遍历输入的每个段
        for i in input().strip().split('.'):
            # 如果是数字，并且该数字对应的整型在[0,256]范围内
            if not (i.isdigit() and 0 <= int(i) <= 255):
                print('NO')
                break
        # 如果上面的遍历没有触发break，则执行这个else，打印YES
        else:
            print('YES')
    except:
        break

let ip = readline()
let ips = ip.split('.')
console.log(ips.length===4 && ips.every(el=> {
  return parseInt(el).toString() === el && parseInt(el)<=255 && parseInt(el)>=0
})? 'YES' : 'NO')

import java.util.Scanner;

/**
* 练习写个正则表达式
*/
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            String s = scanner.nextLine();
            solution(s);
        }
    }

    /**
     * ip地址判断
     * <p>
     * 正则表达式
     * 0-199: (0|1)?[0-9]{1,2}
     * 200-249: 2[1-4][0-9]
     * 250-255: 25[0-5]
     * 0-255: (((0|1)?[0-9]{1,2})|(2[1-4][0-9])|(25[0-5]))
     * ip: ((((0|1)?[0-9]{1,2})|(2[1-4][0-9])|(25[0-5]))\\.){3}(((0|1)?[0-9]{1,2})|(2[1-4][0-9])|(25[0-5]))
     *
     * @param ip
     */
    public static void solution(String ip) {
        boolean matches = ip.matches("((((0|1)?[0-9]{1,2})|(2[1-4][0-9])|(25[0-5]))\\.){3}(((0|1)?[0-9]{1,2})|(2[1-4][0-9])|(25[0-5]))");
        System.out.println(matches ? "YES" : "NO");
    }
}

#include <bits/stdc++.h>

using namespace std;

int main(){
    unsigned int a,b,c,d;
    char ch;
    while(cin >> a >> ch >> b >> ch >> c >> ch >> d){
        if((a == 0 && b == 0 && c == 0 && d == 0) || (a == 255 && b == 255 && c == 255 && d == 255)){
            cout << "NO" << endl;
        } else if((a<0 || a > 255) || (b<0 || b > 255) || (c<0 || c > 255) || (d<0 || d > 255)){
            cout << "NO" << endl;
        } else {
            cout << "YES" << endl;
        }
    }
}

#include <bits/stdc++.h>
using namespace std;

int main(){
    int a,b,c,d;
    while(4==scanf("%d.%d.%d.%d",&a,&b,&c,&d)){
        if(0<=a&&a<=255&&0<=b&&b<=255&&0<=c&&c<=255&&0<=d&&d<=255) cout << "YES" << endl;
        else cout << "NO" << endl;
    }
    return 0;
}

while True:
    try:
        ls=list(input().split('.'))
        if len(ls)!=4:
            print('NO')
        else:
            x=True
            for i in ls:
                #print(i)
                if int(i)<=255 and int(i)>=0:
                    continue
                else:
                    x=False
            if x:
                print('YES')
            else:
                print('NO')
    except:
        break

import java.util.Scanner;
public class Main{     public static void main(String[] args) {         Scanner sc = new Scanner(System.in);         while (sc.hasNext()) {             String string = sc.nextLine();             String[] arrs = string.split("\\.");             String illegal="YES";
          for(int i=0;i<arrs.length;i++)
          {
              if(Integer.parseInt(arrs[i])>255||Integer.parseInt(arrs[i])<0)
              {
                  illegal="NO";
                  break;
              }
          }             System.out.println(illegal);         }     }
}

import java.util.*;

public class Main {

    public static void main(String[] args) throws Exception {
        Scanner jin = new Scanner(System.in);
        while (jin.hasNext()) {
            String s = jin.nextLine();
            boolean flag = true;
            String[] strings = s.split("\\.");
            for (int i = 0; i < strings.length; i++) {
                int num = Integer.valueOf(strings[i]);
                if (!(num >= 0 & num <= 255)) {
                    flag = false;
                }
            }
            if (flag) {
                System.out.println("YES");
            } else {
                System.out.println("NO");
            }
        }
    }
}

import java.util.Scanner;
public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
            while(sc.hasNext()){
                String line = sc.nextLine();
                boolean flag = true;
                if(line.contains(" ")) {
                    flag = false;
                } else {
                    String[] ips = line.split("\\.");
                    for(int i=0; i<ips.length; i++) {
                        if(Integer.valueOf(ips[i])<0 || Integer.valueOf(ips[i])>255) {
                            flag = false;
                            break;
                        }
                    }
                }
                if(flag) {
                    System.out.println("YES");
                } else {
                    System.out.println("NO");
                }
            }
    }
}

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <cstring>
#include <string>
#include <cmath>
#include <cctype>
#include <vector>

using namespace std;

int main()
{     int a[4];     char c[3];     while(cin>>a[0]>>c[0]>>a[1]>>c[1]>>a[2]>>c[2]>>a[3])     {         if(c[0]=='.' && c[1]=='.' && c[2]=='.')         {             bool flag = true;             for(int i=0;i<4;i++)                 if(a[i]<0 || a[i]>255)                     flag = false;             if(flag)                 cout<<"YES"<<endl;             else                 cout<<"NO"<<endl;                         }     }     return 0;
}

其实情况太多了。。。

package com.special.spet;

import java.util.Scanner;

/** 
*
* @author special
* @date 2017年12月9日 上午9:46:31
*/
public class Pro89 {
    public static boolean isNum(char ch) { return ch >= '0' && ch <= '9'; }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner input = new Scanner(System.in);
        while(input.hasNext()){
            String str = input.nextLine();
            String[] ips = str.split("\\.");
            if(ips.length != 4)
                System.out.println("NO");
            else{
                boolean flag = false;
                for(int i = 0; i < ips.length; i++){
                    int temp = 0;
                    int index = 0;
                    while(index < ips[i].length() && isNum(ips[i].charAt(index)))
                        temp = temp * 10 + (ips[i].charAt(index++) - '0');
                    if(index < ips[i].length() || temp > 255){ //若是某个段位出现非数字或者范围超出跳出
                        flag = true;
                        break;
                    }
                }
                if(!flag) System.out.println("YES");
                else      System.out.println("NO");
            }
        }
    }

}

while(line=readline()){
    const ips = line.split('.');
    let res = 'YES';
    for (let i = 0; i < 4; i++) {
        if (ips[i] > 255 || ips[i] < 0) {
            res = 'NO';
        }
    }
    print(res);
}

	

//stringstream 用完之后要清空，否则下次使用之前的值还是保存在那里 #include <iostream>
#include <string>
#include <sstream>

using namespace std;

int main(){
	string str;
	while(getline(cin,str)){
		if(str.find(' ') != string::npos){//首先判断是否存在空格
			cout<<"NO"<<endl;
			continue;
		}
		stringstream ss;
		int flag=0;
		while(!str.empty()){//用‘.‘分割开，各个数字大小是否在限定范围内
			int a,b;
			a=str.find('.');
			if(a!=-1){
				ss<<str.substr(0,a);
				ss>>b;
                ss.clear();
				if(b<0 || b>256){
					cout<<"NO"<<endl;
					flag=1;
					break;
				}
				str=str.substr(a+1,str.length());
			}
			else{//最后一个无法分割，可以直接使用
				ss<<str;
				ss>>b;
                ss.clear();
				if(b<0 || b>256){
					cout<<"NO"<<endl;
					flag=1;
					break;
				}
				str="";
			}
		}
		if(flag==0)
			cout<<"YES"<<endl;
	}
	return 0;
}