题解 | #IP地址#

#include <iostream>
#include <string>

using namespace std;

int main() {
    string id;
    while (cin >> id) {
        bool flag = false;
        id += '.';
        for (int i = 0, j = 0, k = 0, n = id.size(); j < n; ++j) {
            if (id[j] != '.') continue;
            else {
                int val = stoi(id.substr(i, j - i));
                if (0 > val || 255 < val) break;
                i = j + 1;
                if (++k == 4) flag = true; 
            }
        }
        cout << (flag ? "Yes!" : "No!") << endl;
    }
}
// 64 位输出请用 printf("%lld")