Question

USE JAVA PLEASE

Use recursion to implement a method

public static int indexOf(String text, String str)
that returns the starting position of the first substring of the text that matches str.

Return –1 if str is not a substring of the text.

For example, s.indexOf("Mississippi", "sip") returns 6.

Hint: You must keep track of how far the match is from the beginning of the text. Make that value a parameter variable of a helper method.

Answer 1

Ans)

public int indexOf(String text, String str){

if (text.substring(0,str.length()).equals(str.substring(0,str.length()))){ // if first character
return 0;
}

if (text.length() <= 0 || str.length() <= 0)
return -1;

if (str.length() > text.length()){
return -1;
}

if (text.length() <= 1)
return -1;

return (1 + indexOf(text.substring(1,text.length()), str.substring(0,str.length())));

// check second characracter and so on
}

/* PROGRAM */

public class Test {

public int indexOf(String text, String str){

if (text.substring(0,str.length()).equals(str.substring(0,str.length()))){
return 0;
}

if (text.length() <= 0 || str.length() <= 0)
return -1;

if (str.length() > text.length()){
return -1;
}

if (text.length() <= 1)
return -1;

return (1 + indexOf(text.substring(1,text.length()), str.substring(0,str.length())));
}
public static void main(String[] args) {
Test s = new Test();
System.out.println(s.indexOf("Mississippi", "sip"));
}   
}

/* PLEASE UPVOTE */