Question

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.

Difficulty:Easy

Category:Hash-Table, Bit-Manipulation

Analyze

Solution

class Solution {
 public:
  char findTheDifference(string s, string t) {
    unordered_map<char, int> m_;
    for (char& c : s) ++m_[c];
    for (char& c : t)
      if (--m_[c] < 0) return c;
    return 'A';
  }
};