[LeetCode] NO. 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.

[题目解析] 根据题意，字符串中只含有小写字母，则可以用一个26位的数组表示map结构，记录对应字符串的字符和出现次数。如下。

   public char findTheDifference(String s, String t) {
       int[] hash = new int[26];
       char[] sarray = s.toCharArray();
       char[] tarray = t.toCharArray();
       for(int i = 0; i < s.length(); i++){
    	   int num = sarray[i] - ‘a‘;
    	   hash[num]++;
       }
       for(int i = 0; i < t.length(); i++){
    	   int tnum = tarray[i] - ‘a‘;
    	   hash[tnum]--;
    	   if(hash[tnum] < 0){
    		   return (char) ((char)tnum+‘a‘);
    	   }
       }
       return ‘-‘;
   }