Leetcode 389 Find the Difference

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.

题目大意：

给定两个字符串s和t，都只包含小写字母。

字符串t由字符串s打乱顺序并且额外在随机位置添加一个字母组成。

寻找t中新增的那个字母。

测试用例如题目描述。

方法一：利用Hash表，

char findTheDifference(string s, string t) {
        int a[26] = {0}, lens = s.length(), lent = t.length(), i;
        for(i = 0; i < lens; i++)
            a[s[i] - 'a']++;
        for(i = 0; i < lent; i++)
            if(a[t[i] - 'a'] <= 0)
                break;
            else
                a[t[i] - 'a']--;
        return t[i];
    }

方法二：两个字符串加起来只有一个字符时单独的。。利用异或运算

char findTheDifference(string s, string t) {
        int ans = 0, i, lens = s.length(), lent = t.length();
        for(i = 0; i < lens; i++)
            ans ^= (s[i] - 'a');
        for(i = 0; i < lent; i++)
            ans ^= (t[i] - 'a');
        return 'a' + ans;
    }