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.
使用库里的 hashMap 可能有点慢 ，自己写一个用字母值做映射的count数组就好了。
class Solution {
public char findTheDifference(String s, String t) {
int[] count = new int [26];
char result=' ' ;
for(int i = 0 ;i<s.length();i++)
{
int index = (int)(s.charAt(i)-'a');
count[index]++;
}
for(int i = 0 ;i<t.length();i++)
{
int index = (int)(t.charAt(i)-'a');
if(count[index]>0)
count[index]--;
else
result=t.charAt(i);
}
return result;
}
}
