UniqueCharString.java

//This Program is to find out whether String contains all the unique characters 
//With out using any additional data structures
public class UniqueCharString {
	private String ip;

	public UniqueCharString(String ip) {
		this.ip = ip;
	}

	// method 1 : When characters are not ASCII but could be anything alphabets
	// or special characters
	// Time Complexity : O(n)
	// Space Complexity : O(1)

	//
	public Boolean UniChars() {
		Boolean[] bln = new Boolean[256];
		for (int i = 0; i < 256; i++) {
			bln[i] = false;
		}
		for (int i = 0; i < ip.length(); i++) {
			char a = ip.charAt(i);
			if (bln[a] == true) {
				return false;
			} else {
				bln[a] = true;
			}
		}

		return true;
	}

	// method 2: Sort the array and do the linear scan to find out whether
	// string
	// contains unique elements or not
	// Time Complexity : O(nLogn)
	// Space Complexity : O(n)

	public Boolean UniqueCharSorting() {
		char[] a = ip.toCharArray();
		java.util.Arrays.sort(a);
		String tmp = new String(a);
		for (int i = 1; i < tmp.length(); i++) {
			char t = tmp.charAt(i - 1);
			if (t == tmp.charAt(i)) {
				return false;
			}
		}
		return true;
	}

	public static void main(String args[]) {
		String a = "Sumit_Jain";
		UniqueCharString u = new UniqueCharString(a);
		System.out.println("Method 1 : Does String ' " + a
				+ " ' has all unique characters :" + u.UniChars());

		a = "Sumit";
		u = new UniqueCharString(a);
		System.out.println("Method 1 : Does String ' " + a
				+ " ' has all unique characters :" + u.UniChars());

		a = "Sumit_Jain";
		u = new UniqueCharString(a);
		System.out.println("Method 2 : Does String ' " + a
				+ " ' has all unique characters :" + u.UniqueCharSorting());

		a = "Sumit";
		u = new UniqueCharString(a);
		System.out.println("Method 2 : Does String ' " + a
				+ " ' has all unique characters :" + u.UniqueCharSorting());
	}

}