题解 | IP地址

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

//判断是否为数字字符
bool isnum(char a)
{
    return a>='0'&&a<='9';
}

//将字符转换为数字
int chartonum(char a)
{
    return a-'0';
}

int main()
{
    string str;
    while(getline(cin,str))
    {
        int len = str.length();
        int i = 0,flag = 0;
        while(i<len)
        {
            int sum = 0;
            if(isnum(str[i]))
            {
                while(isnum(str[i])&&i<len)
                {
                    sum = sum*10+str[i]-'0';
                    i++;
                }
                if(sum<0||sum>255)
                {
                    cout<<"No!"<<endl;
                    flag = 1;
                    break;
                }
            }
            else {
            i++;
            }
        }
        if(flag == 0)
        {
            cout<<"Yes!"<<endl;

        }

    }
    return 0;
}