Given two strings s and t which consist of only lowercase letters.

String t is generated by random shuffling string s and then add one more letter at a random position.

Find the letter that was added in t.

Example:

Input:s = "abcd"t = "abcde"Output:eExplanation:'e' is the letter that was added.

public class Solution {    public static char findTheDifference(String s, String t) {    	if (s == null || t.length() == 0)     		return t.charAt(0);    	if (t == null || t.length() == 0)     		return s.charAt(0);    	if (s == null && t == null)    		return 0;    	int[] a = new int[30];    	char[] tChars = t.toCharArray();    	char[] sChars = s.toCharArray();    	int sLength = s.length();    	int tLength = t.length();    	if (sLength > tLength) {    		for (int i = 0; i < sChars.length; i++) {    			 if (a[sChars[i] - 97] != 0)    				 a[sChars[i] - 97] = ++(a[sChars[i] - 97]);    			 else    				 a[sChars[i] - 97] = 2;    		}    		for (int i = 0; i < tChars.length; i++) {    			a[tChars[i] - 97] = --(a[tChars[i] - 97]);    		    }    	} else {    		for (int i = 0; i < tChars.length; i++) {    			if (a[tChars[i] - 97] != 0)   				 a[tChars[i] - 97] = ++(a[tChars[i] - 97]);   			 else   				 a[tChars[i] - 97] = 2;   		    }    		for (int i = 0; i < sChars.length; i++) {    			a[sChars[i] - 97] = --(a[sChars[i] - 97]);    		    }    	}    	for (int i = 0; i < 30; i ++) {    		if (a[i] >= 2) {    			return (char) (i + 97);    		}     	}    	return 0;    }}