Implement strstr

Problem Statement - link #

Your task is to implement the function strstr. The function takes two strings as arguments (s,x) and locates the occurrence of the string x in the string s. The function returns and integer denoting the first occurrence of the string x in s (0 based indexing).

Note: You are not allowed to use inbuilt function.

Your Task: You don’t have to take any input. Just complete the strstr() function which takes two strings str, target as an input parameter. The function returns -1 if no match if found else it returns an integer denoting the first occurrence of the x in the string s.

Expected Time Complexity: O(|s|*|x|)
Expected Auxiliary Space: O(1)

Examples #

Example 1:

Input:
s = GeeksForGeeks, x = Fr
Output: -1
Explanation: Fr is not present in the
string GeeksForGeeks as substring.

Example 2:

Input:
s = GeeksForGeeks, x = For
Output: 5
Explanation: For is present as substring
in GeeksForGeeks from index 5 (0 based
indexing).

Constraints #

• 1 <= |S|, |X| <= 100

Solutions #

class Solution{
    public:
    //Function to locate the occurrence of the string x in the string s.
    int strstr(string s, string x)
    {
        //Your code here
        int n = s.size(), m = x.size();
        for(int i=0; i<n; i++){
            if(s[i] == x[0]) {
                int j = 1;
                for(; j<m; j++)
                    if(s[i+j]!=x[j]) break;
                if(j==m) return i;
            }
        }
        return -1;
    }
};