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.
Solution1：Bit Manipulation (Xor)
Time Complexity: O(N) Space Complexity: O(1)
Solution2：Hashmap(count)
Time Complexity: O(N) Space Complexity: O(N)
Solution1 Code：
class Solution {
public char findTheDifference(String s, String t) {
char c = 0;
for (int i = 0; i < s.length(); ++i) {
c ^= s.charAt(i);
}
for (int i = 0; i < t.length(); ++i) {
c ^= t.charAt(i);
}
return c;
}
}
Solution2 Code：
class Solution2 {
public char findTheDifference(String s, String t) {
int alpha[] = new int[26];
for(int i = 0; i < s.length(); i++) {
alpha[s.charAt(i) - 'a']++;
}
for(int i = 0; i < t.length(); i++) {
alpha[t.charAt(i) - 'a']--;
if(alpha[t.charAt(i) - 'a'] < 0) {
return t.charAt(i);
}
}
return 0;
}
}
