LeetCode-in-Java
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
public class Solution {
public String largestPalindromic(String num) {
int[] count = new int[10];
int center = -1;
StringBuilder first = new StringBuilder();
StringBuilder second;
for (char c : num.toCharArray()) {
count[c - '0']++;
}
int c = 0;
for (int i = 9; i >= 0; i--) {
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(String.valueOf(i));
c++;
}
}
second = new StringBuilder(first.toString());
if (center != -1) {
first.append(center);
}
first.append(second.reverse().toString());
return first.length() == 0 ? "0" : first.toString();
}
}