5. Check whether one string is a rotation of another

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5. Check whether one string is a rotation of another


Problem link :- click here


package programs;

public class String__5
{
	
	static Boolean areRotations(String s1, String s2)
	{
		if(  s1.length() != s2.length()  )
			return false;
		
		//method 1
		/*
			String concatenate = s1 + s1;
			if( concatenate.indexOf(s2) != -1 )
				return true;
			return false;
		*/
		
		//method 2
		/*
		 	we will find the index of first character of s2 in s1
		 	using that index we will check if s2 is the rotation of s1
		*/
		
		char x = s2.charAt(0);    //first character
		int index = 0;	    //index of first character
		
		for(int i=0; i<s1.length(); i++)
		{
			if(s1.charAt(i) == x)
			{
				index = i;
				break;	//because one step process
			}
		}
		
		for(int i=0; i<s1.length(); i++)
		{
			if( s1.charAt(i) != s2.charAt(index)  )
				return false;
			index = (index+1) % s1.length();
		}
		return true;
	}

	public static void main(String[] args)
	{
		String s1 = "ABCD";
		String s2 = "CDMB";
		
		Boolean ans = areRotations(s1, s2);
		if(ans)
			System.out.println("s2 is rotation of s1");
		else
			System.out.println("s2 is not rotation of s1");
	}

}

Time complexity :- O(n)
Space complexity :- O(1)

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