389. Find the Difference

389. Find the Difference (Easy)

You are given two strings s and t.

String t is generated by random shuffling string s and then add one more letter at a random position.

Return the letter that was added to t.

 

Example 1:

Input: s = "abcd", t = "abcde"
Output: "e"
Explanation: 'e' is the letter that was added.

Example 2:

Input: s = "", t = "y"
Output: "y"

 

Constraints:

• 0 <= s.length <= 1000
• t.length == s.length + 1
• s and t consist of lowercase English letters.

Companies:
Google

Related Topics:
Hash Table, String, Bit Manipulation, Sorting

Similar Questions:

• Single Number (Easy)

Solution 1. Counting

// OJ: https://leetcode.com/problems/find-the-difference/
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(1)
class Solution {
public:
    char findTheDifference(string s, string t) {
        int cnt[26] = {};
        for (char c : s) cnt[c - 'a']++;
        for (char c : t) {
            if (--cnt[c - 'a'] < 0) return c;
        }
        return 0;
    }
};