Additive sequence.cpp

class Solution
{
public:
    bool isAdditiveSequence(string s)
    {
        int n = s.size();
        int num1 = 0;
        for (int i = 0; i < n / 2; i++)
        {
            num1 = num1 * 10 + (s[i] - '0');
            int num2 = 0;
            for (int j = i + 1; j < n - 1; j++)
            {
                num2 = num2 * 10 + (s[j] - '0');
                int prev2 = num1, prev1 = num2;
                int num = 0;
                int k = j + 1;
                while (k < n)
                {
                    num = num * 10 + (s[k] - '0');
                    if (num == (prev1 + prev2))
                    {
                        prev2 = prev1;
                        prev1 = num;
                        num = 0;
                    }
                    k++;
                }
                if (k == n && num == 0)
                    return 1;
            }
        }
        return 0;
    }
};