Implement strstr using array

Write a program to implement strstr using array.

Algorithm Explanation

	Pass two strings to the utility function.
	Take length of two strings and iterate the string.
	Find the substring from the second string. Return and print the string.

Source Code

package com.dsacode.DataStructre.array;
 
public class StrStrArray {
    public String strStr(String haystack, String needle) {
          
        int needleLen = needle.length();
        int haystackLen = haystack.length();
      
        if (needleLen == haystackLen && needleLen == 0)
            return "";
      
        if (needleLen == 0)
            return haystack;
      
        for (int i = 0; i < haystackLen; i++) {
 
            if (haystackLen - i + 1 < needleLen)
                return null;
      
            int k = i;
            int j = 0;
      
            while (j < needleLen && k < haystackLen && needle.charAt(j) == haystack.charAt(k)) {
                j++;
                k++;
                if (j == needleLen)
                    return haystack.substring(i);
            }
      
        }
      
        return null;
    }
    public static void main(String[] args) {
        StrStrArray s = new StrStrArray();
        System.out.println("Implement strstr function  and pass 'Helloworld' and 'vlow' arguments");
        String strres = s.strStr("Helloworld", "low");
         
        System.out.println("Result String: "+ strres);
 
    }
 
}

Output

Implement strstr function and pass 'Helloworld' and 'vlow' arguments
Result String: loworld