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.

s是一串随机的字符串，将s的每个字母打乱后，再加入一个字母，形成字符串t，问加入的是哪个字母

Bit Manipulation:

C++(3ms):

class Solution {
public:
    char findTheDifference(string s, string t) {
        int res = t[t.size()-1] ;
        for(int i = 0 ; i < s.size() ; i++){
            res ^= s[i] ^ t[i] ;
        }
        return (char)res ;
    }
};

java(7ms):

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

java（6ms）：

public class Solution {
    public char findTheDifference(String s, String t) {
        char[] ss = s.toCharArray() ;
        char[] tt = t.toCharArray() ;
        int slen = s.length() ;
        int sum = 0 ;
        int i ;
        for (i = 0 ; i < slen ; i++){
            sum -= (int)ss[i] ;
            sum += (int)tt[i] ;
        }
        sum += (int)tt[i] ;
        
        return (char)sum;
    }
}

C++(3ms):

class Solution {
public:
    char findTheDifference(string s, string t) {
        int sum = 0 ;
        int i ;
        for(i = 0 ; i < s.size() ; i++){
            sum -= (int)s[i] ;
            sum += (int)t[i] ;
        }
        sum += (int)t[i] ;
        return (char)sum ;
    }
};