题解 | #合法IP#

//容易遗漏的点在于数字串中有非法字符或字符'0'后跟字符的情况
//还有就是IP只有三个

#include <iostream>
#include <sstream>
#include <string>
#include <deque>
using namespace std;

int main(){
    string inputstr;
    cin >> inputstr;
    inputstr+=".";
    string tmp;
    int count = 0;
    for(int i = 0;i<inputstr.size();++i){
        
        if(tmp == "" && ((!isdigit(inputstr[i])) || (inputstr[i] == '0' && inputstr[i+1] != '.'))){
            cout << "NO" << endl;
            return 0;
        }
        if(inputstr[i] == '.'){
            if(stoi(tmp)<=255 && stoi(tmp)>= 0){
                tmp = "";
                ++count;
                continue;
            }
            else{
                cout << "NO" << endl;
                return 0;
            }
        }
        tmp += inputstr[i];
    }
    if(count == 4)cout << "YES" << endl;
    else cout << "NO" << endl;
    return 0;
}