744. Find Smallest Letter Greater Than Target

Easy

You are given an array of characters letters that is sorted in non-decreasing order, and a character target. There are at least two different characters in letters.

Return the smallest character in letters that is lexicographically greater than target. If such a character does not exist, return the first character in letters.

Example 1:

Input: letters = ["c","f","j"], target = "a"
Output:
 "c"
Explanation:
 The smallest character that is lexicographically greater than 'a' in letters is 'c'.

Example 2:

Input: letters = ["c","f","j"], target = "c"
Output:
 "f"
Explanation:
 The smallest character that is lexicographically greater than 'c' in letters is 'f'.

Example 3:

Input: letters = ["x","x","y","y"], target = "z"
Output:
 "x"
Explanation:
 There are no characters in letters that is lexicographically greater than 'z' so we return letters[0].

Constraints:

• 2 <= letters.length <= 104

• letters[i] is a lowercase English letter.

• letters is sorted in non-decreasing order.

• letters contains at least two different characters.

• target is a lowercase English letter.

解題

O(n) 暴力解

func nextGreatestLetter(letters []byte, target byte) byte {
    ans := byte('|')

    for _, letter := range letters {
        if letter > target && letter < ans {
            ans = letter
        }
    }

    if ans == byte('|') { return letters[0] }

    return ans
}