16.力扣c++刷题--＞找出字符串中第一个匹配的子串

#include
#include
#include
#include
#include
#include
using namespace std;


  
class Solution {
public:
    int strStr(string haystack, string needle)
    {
        int j = 0;
        for (int i = 0; i < haystack.size(); i++)
        {
            if (haystack[i] == needle[j])
            {
                if (j == (needle.size() - 1))
                {
                    return (i - j);
                }
                j++;
            }
            else
            {
                j = 0;
            }
        }
        return -1;
    }
};

int main()
{

    Solution a;
    string haystack = "sadbutsad";
    string needle = "db";
    cout << a.strStr(haystack, needle) << endl;
   
    return 0;
}