华为机试：合法IP

#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
using namespace std;

int main() {
    string ip;
    cin >> ip;
    if (count(ip.begin(), ip.end(), '.') < 3 || count(ip.begin(), ip.end(), '.') > 3) {
        cout << "NO" << endl;
        return 0;
    }
    string temp;
    vector<int> IP;
    for (char ch : ip) {
        if (ch >= '0' && ch <= '9') {
            temp.push_back(ch);
        }
        else if (ch == '.') {
            if (!temp.empty() && !(temp.length() > 1 && temp[0] == '0')) {
                IP.push_back(stoi(temp));
                temp.clear();
            }
        }
        else {
            cout << "NO" << endl;
            return 0;
        }
    }
    if (!temp.empty() && !(temp.length() > 1 && temp[0] == '0')) IP.push_back(stoi(temp));
    if (IP.size() < 4 || IP.size() > 4) {
        cout << "NO" << endl;
        return 0;
    }
    for (int i = 0; i < IP.size(); i++) {
        if (IP[i] < 0 || IP[i] > 255) {
            cout << "NO" << endl;
            return 0;
        }
    }
    cout << "YES" << endl;
    return 0;
}