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"

 

Constraints:

• 0 <= s.length <= 1000
• t.length == s.length + 1
• s and t consist of lowercase 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 ' ';
    }
}

Rust

impl Solution {
    pub fn find_the_difference(s: String, t: String) -> char {
        let s = s.as_bytes();
        let t = t.as_bytes();
        let n = s.len();
        let mut count = [0; 26];
        for i in 0..n {
            count[(s[i] - b'a') as usize] -= 1;
            count[(t[i] - b'a') as usize] += 1;
        }
        let mut res = *t.last().unwrap();
        for i in 0..26 {
            if count[i] == 1 {
                res = (i as u8) + b'a';
                break;
            }
        }
        char::from(res)
    }
}

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