LeetCode in Kotlin
2384. Largest Palindromic Number
Medium
You are given a string num consisting of digits only.
Return the largest palindromic integer (in the form of a string) that can be formed using digits taken from num. It should not contain leading zeroes.
Notes:
- You do not need to use all the digits of
num, but you must use at least one digit. - The digits can be reordered.
Example 1:
Input: num = “444947137”
Output: “7449447”
Explanation:
Use the digits “4449477” from “444947137” to form the palindromic integer “7449447”.
It can be shown that “7449447” is the largest palindromic integer that can be formed.
Example 2:
Input: num = “00009”
Output: “9”
Explanation:
It can be shown that “9” is the largest palindromic integer that can be formed.
Note that the integer returned should not contain leading zeroes.
Constraints:
1 <= num.length <= 105numconsists of digits.
Solution
class Solution {
fun largestPalindromic(num: String): String {
val count = IntArray(10)
var center = -1
val first = StringBuilder()
for (c in num.toCharArray()) {
count[c.code - '0'.code]++
}
var c: Int
for (i in 9 downTo 0) {
c = 0
if (count[i] % 2 == 1 && center == -1) {
center = i
}
if (first.length == 0 && i == 0) {
continue
}
while (c < count[i] / 2) {
first.append(i.toString())
c++
}
}
val second: StringBuilder = StringBuilder(first.toString())
if (center != -1) {
first.append(center)
}
first.append(second.reverse().toString())
return if (first.length == 0) "0" else first.toString()
}
}