# 389 Find the Difference

### Problem:

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:
e

Explanation:
'e' is the letter that was added.
``````

### Solutions:

``````public class Solution {
public char findTheDifference(String s, String t) {
HashMap<Character, Integer> chars = new HashMap<Character, Integer>();
for (int i = 0; i < s.length(); i ++) {
char c = s.charAt(i);
if (!chars.containsKey(c)) {
chars.put(c, 0);
}
chars.put(c, chars.get(c) + 1);
}
for (int i = 0; i < t.length(); i ++) {
char c = t.charAt(i);
if (!chars.containsKey(c)) {
return c;
}
if (chars.get(c) == 0) {
return c;
}
chars.put(c, chars.get(c) - 1);
}
return ' ';
}
}
``````
``````public class Solution {
public char findTheDifference(String s, String t) {
char[] sc = s.toCharArray();
char[] tc = t.toCharArray();
Arrays.sort(sc);
Arrays.sort(tc);
for (int i = 0; i < sc.length; i ++) {
if (sc[i] != tc[i]) {
return tc[i];
}
}
return tc[tc.length - 1];
}
}
``````
``````public class Solution {
public char findTheDifference(String s, String t) {
int res = 0;
for (int i = 0; i < s.length(); i ++) {
res = res^s.charAt(i);
res = res^t.charAt(i);
}
res = res^t.charAt(t.length() - 1);
return (char)res;
}
}
``````
``````public class Solution {
public char findTheDifference(String s, String t) {
int res = 0;
for (int i = 0; i < s.length(); i ++) {
res = res - s.charAt(i);
res = res + t.charAt(i);
}
res = res + t.charAt(t.length() - 1);
return (char)res;
}
}
``````