题解 | #IP地址#

#include <bits/stdc++.h>
using namespace std;
int main()
{
    string ip;
    while(cin>>ip)
    {
        int len = ip.length();
        stack <int> stk;
        int flag = 0;
        for(int i = 0; i < len ; i ++)
        {
            if(ip[i]!='.')
            {
                stk.push(ip[i]-'0');
            }
            else if(ip[i] == '.')
            {
                int sum = 0;
                int times = 0;
                while(!stk.empty())
                {
                    int temp = stk.top();
                    sum += temp * pow(10,times);
                    times++;
                    stk.pop();
                }
                if(!(sum>=0&&sum<=255))
                {
                    flag = 1;
                }
            }
        }
        int sum = 0;
        int times = 0;
        while(!stk.empty())
        {
            int temp = stk.top();
            sum += temp * pow(10,times);
            times++;
            stk.pop();
        }
        if(!(sum>=0&&sum<=255))
        {
            flag = 1;
        }
        if(flag == 0)
        cout << "Yes!" << endl;
        else
        cout << "No!" << endl;
    }
    
    return 0;
    
    
}