# 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:

```java
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 ' ';
    }
}
```

```java
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];
    }
}
```

```java
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;
    }
}
```

```java
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;
    }
}
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://ugopireddy.gitbook.io/leet-code-solutions/solutions-351---400/389-find-the-difference.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.