389. Find the Difference

题目：

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.

链接：https://leetcode.com/problems/find-the-difference/#/description

3/20/2017

最后一行如何返回会更好？

public class Solution {
    public char findTheDifference(String s, String t) {
        int[] cs = new int[256];
        int[] ct = new int[256];

        for (int i = 0; i < s.length(); i++)
            cs[s.charAt(i)]++;
        for (int i = 0; i < t.length(); i++)
            ct[t.charAt(i)]++;
        for (int i = 0; i < 256; i++) {
            if (ct[(char)i] > cs[(char)i]) return (char)i;
        }
        return '0';
    }
}

别人的非常好的方法，位运算：

https://discuss.leetcode.com/topic/55912/java-solution-using-bit-manipulation

public char findTheDifference(String s, String t) {
    int n = t.length();
    char c = t.charAt(n - 1);
    for (int i = 0; i < n - 1; ++i) {
        c ^= s.charAt(i);
        c ^= t.charAt(i);
    }
    return c;
}

类似的用char对int的值

public char findTheDifference(String s, String t) {
        int charCode = t.charAt(s.length());
        // Iterate through both strings and char codes
        for (int i = 0; i < s.length(); ++i) {
              charCode -= (int)s.charAt(i);
              charCode += (int)t.charAt(i); 
        }
        return (char)charCode;
    }