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:
1 public class Solution { 2 public char findTheDifference(String s, String t) { 3 char c = t.charAt(t.length()-1); 4 for(int i = s.length()-1; i>=0; i--){ 5 c ^= s.charAt(i); 6 c ^= t.charAt(i); 7 } 8 return c; 9 } 10 }
也可以直接采用char code 得出diff
Time Complexity: O(t.length()). Space: O(1).
AV Java:
1 public class Solution { 2 public char findTheDifference(String s, String t) { 3 int charCodeDiff = 0; 4 for(int i = 0; i<s.length(); i++){ 5 charCodeDiff -= (int)s.charAt(i); 6 charCodeDiff += (int)t.charAt(i); 7 } 8 charCodeDiff += t.charAt(t.length()-1); 9 return (char)charCodeDiff; 10 } 11 }
原文：http://www.cnblogs.com/Dylan-Java-NYC/p/6240686.html