Reorganize String

import java.util.*;

class Solution {
    public String reorganizeString(String s) {
        int[] freq = new int[26];
        for (char c : s.toCharArray()) freq[c - 'a']++;
        PriorityQueue<int[]> pq = new PriorityQueue<>((a, b) -> b[1] - a[1]);
        for (int i = 0; i < 26; i++) if (freq[i] > 0) pq.offer(new int[]{i, freq[i]});
        StringBuilder sb = new StringBuilder();
        while (pq.size() >= 2) {
            int[] first = pq.poll(), second = pq.poll();
            sb.append((char)(first[0] + 'a'));
            sb.append((char)(second[0] + 'a'));
            if (--first[1] > 0) pq.offer(first);
            if (--second[1] > 0) pq.offer(second);
        }
        if (!pq.isEmpty()) {
            int[] last = pq.poll();
            if (last[1] > 1) return "";
            sb.append((char)(last[0] + 'a'));
        }
        return sb.toString();
    }
}