389. Find the Difference

Problem¶

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.

Solve¶

Bit operator xor¶

O(n)

I just consider string as a full binary array, two same bytes xor each other will return 0.
Thus, xor every byte in s and t array will equivalent to `0 xor 0 xor … xor 0 xor = .

func findTheDifference(s string, t string) byte {
    var res byte = 0
    for i := 0; i < len(s); i ++ {
        res = res ^ s[i]
    }
    for i := 0; i < len(t); i ++ {
        res = res ^ t[i]
    }
    return res
}