0028. Find the Index of the First Occurrence in a String.cpp

class Solution
{
public:
    int strStr(string haystack, string needle)
    {
        if (needle.size() <= haystack.size())
        {
            for (int i = 0; i <= haystack.size() - needle.size(); ++i)
            {
                for (int j = 0; j < needle.size(); ++j)
                {
                    if (needle[j] != haystack[i + j])
                    {
                         break;
                    }

                    if (j == needle.size() - 1)
                    {
                        return i;
                    }
                }
            }
        }

        return -1;
    }
};