LeetCode 389. Find the Difference

原题链接在这里：https://leetcode.com/problems/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.

题解：

可用Bit Manipulation, t的每个char ^ s的每个char, 剩下的就是diff.

Time Complexity: O(t.length()). Space: O(1).

AC Java:

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

AC C++:

class Solution {
public:
    char findTheDifference(string s, string t) {
        char res = 0;
        for(char c : s){
            res ^= c;
        }

        for(char c : t){
            res ^= c;
        }

        return res;
    }
};

也可以直接采用char code 得出diff

Time Complexity: O(t.length()). Space: O(1).

AV Java:

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

AC C++:

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

        return t[n];
    }
};

类似Single Number.