Assume you have a method isSubstring which checks if one word is a substring of another. Given two string s1 and s2, write code to check if s2 is a roatation of sq using only one call ot isSubstring (eg., "waterbottle" is a rotation of "erbottlewat").

FindingIfSubstring.java

package com.interview.coding.crack;

public class FindingIfSubstring {

	public boolean isSubstring(char a[], char b[])
	{
		int joint = 0;
		int indexer = 0;
		boolean flag = false;
		if(a.length != b.length)
			return false;
		
		/*
		char[] a = {'w','a','t','e','r','b','o','t','t','l','e'};
		char[] b = {'e','r','b','o','t','t','l','e','w','a','t'};
		char[] c = {'e','a','t','e','r','b','o','t','t','l','e'};
		char[] d = {'e','r','b','o','t','t','l','e','e','a','t'};
		*/
		
		/*
		 * First track the index at which the string is rotated
		 */
		for(int i = 0; i < a.length; i++)
		{
			if(a[i] != b[indexer])
			{
				joint = i+1;
			}
			else
			{
				indexer++;
			}
		}
		
		System.out.println("Rotated at index " + joint);
		
		/*
		 * Start from the beginning of roatation index of the 1st string and the end of of the
		 * 2nd string. Find of all the characters till the beginning of 1st string, match. 
		 */
		indexer = joint - 1;
		int len = b.length;
		for(int i = 0; i < joint; i++)
		{
			
			if(a[indexer] == b[len - 1 - i])
				flag = true;
			else
				flag = false;
			indexer--;
		}
		return flag;
	}
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		char[] a = {'w','a','t','e','r','b','o','t','t','l','e'};
		char[] b = {'e','r','b','o','t','t','l','e','w','a','t'};
		char[] c = {'e','a','t','e','r','b','o','t','t','l','e'};
		char[] d = {'e','r','b','o','t','t','l','e','e','a','t'};
		
		FindingIfSubstring fis = new FindingIfSubstring();
		if(fis.isSubstring(a, b))
			System.out.println("Yes, " + a + " and "+ b + " are substrings");
		else
			System.out.println("Nope, " + a.toString() + " and "+ b.toString() + " are not substrings");
		
		if(fis.isSubstring(a, c))
			System.out.println("Yes, " + a.toString() + " and "+ b.toString() + " are substrings");
		else
			System.out.println("Nope, " + a.toString() + " and "+ b.toString() + " are not substrings");
		
		if(fis.isSubstring(c, d))
			System.out.println("Yes, " + a.toString() + " and "+ b.toString() + " are substrings");
		else
			System.out.println("Nope, " + a.toString() + " and "+ b.toString() + " are not substrings");
	}

}