LeetCode in Kotlin
2309. Greatest English Letter in Upper and Lower Case
Easy
Given a string of English letters s, return the greatest English letter which occurs as both a lowercase and uppercase letter in s. The returned letter should be in uppercase. If no such letter exists, return an empty string.
An English letter b is greater than another letter a if b appears after a in the English alphabet.
Example 1:
Input: s = “lEeTcOdE”
Output: “E”
Explanation:
The letter ‘E’ is the only letter to appear in both lower and upper case.
Example 2:
Input: s = “arRAzFif”
Output: “R”
Explanation:
The letter ‘R’ is the greatest letter to appear in both lower and upper case.
Note that ‘A’ and ‘F’ also appear in both lower and upper case, but ‘R’ is greater than ‘F’ or ‘A’.
Example 3:
Input: s = “AbCdEfGhIjK”
Output: “”
Explanation: There is no letter that appears in both lower and upper case.
Constraints:
1 <= s.length <= 1000sconsists of lowercase and uppercase English letters.
Solution
class Solution {
fun greatestLetter(s: String): String {
var gt = ' '
val sA = BooleanArray(26)
val uA = BooleanArray(26)
for (ch in s.toCharArray()) {
var i: Int
if (ch in 'A'..'Z') {
i = ch.code - 'A'.code
uA[i] = true
} else {
i = ch.code - 'a'.code
sA[i] = true
}
if (uA[i] == sA[i] && gt.code < 'A'.code + i) {
gt = ('A'.code + i).toChar()
}
}
return if (gt == ' ') "" else gt.toString() + ""
}
}