README_EN.md

389. Find the Difference

中文文档

Description

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"

Example 3:

Input: s = "a", t = "aa"
Output: "a"

Example 4:

Input: s = "ae", t = "aea"
Output: "a"

 

Constraints:

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

Solutions

Python3

class Solution:
    def findTheDifference(self, s: str, t: str) -> str:
        counter = Counter(s)
        for c in t:
            if counter[c] <= 0:
                return c
            counter[c] -= 1
        return None

Java

class Solution {
    public char findTheDifference(String s, String t) {
        int[] counter = new int[26];
        for (int i = 0; i < s.length(); ++i) {
            int index = s.charAt(i) - 'a';
            ++counter[index];
        }
        for (int i = 0; i < t.length(); ++i) {
            int index = t.charAt(i) - 'a';
            if (counter[index] <= 0) {
                return t.charAt(i);
            }
            --counter[index];
        }
        return ' ';
    }
}

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