0306.cpp

class Solution {
  public:
    bool isAdditiveNumber(const string &num) {
        for (int i = 1; i < num.size(); i++) {
            long num1 = stol(num.substr(0, i));
            for (int j = i + 1; j < num.size(); j++) {
                long n1 = num1, n2 = stol(num.substr(i, j - i)), n3;
                int next = j;
                while (next < num.size()) {
                    const string pre = to_string(n3 = n1 + n2);

                    auto res = std::mismatch(pre.begin(), pre.end(), num.substr(next).begin());
                    if (res.first != pre.end()) break;

                    next += pre.size();
                    n1 = n2, n2 = n3;
                }
                if (next == num.size()) return true;
                if (num[i] == '0') break;
            }
            if (num[0] == '0') break;
        }
        return false;
    }
};