389. Find the Difference

Posted 2020-08-11 Machelsky

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.

思路：sort一下char array，然后从头比较是不是char一样，如果都一样。那就是t的最后一个字母。

public class Solution {
    public char findTheDifference(String s, String t) {
        char[] schar=s.toCharArray();
        char[] tchar=t.toCharArray();
        Arrays.sort(schar);
        Arrays.sort(tchar);
        
        for(int i=0;i<schar.length;i++)
        {
            if(schar[i]!=tchar[i])
            {
                return tchar[i];
            }
        }
        return tchar[tchar.length-1];
    }
}

Solution2: 用xor X^X=0; X^0=X

两个string全部char xor之后最后肯定剩X^0=X就是我们想要的。

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