28_Find_the_Index_of_the_First_Occurrence_in_a_String.cpp

class Solution {
public:
    int strStr(string haystack, string needle) {
        int m = haystack.length();
    int n = needle.length();

    if (n == 0) {
        return 0; 
    }

    if (m < n) {
        return -1; 
    }

    for (int i = 0; i <= m - n; ++i) {
        int j;
        for (j = 0; j < n; ++j) {
            if (haystack[i + j] != needle[j]) {
                break;
            }
        }

        if (j == n) {
            return i; 
        }
    }

    return -1; 
    }
};