longestDiverseString.java

class Solution {
    public String longestDiverseString(int a, int b, int c) {
        PriorityQueue<int[]> pq = new PriorityQueue<>(
            (x, y) -> y[1] - x[1]
        );

        if (a > 0) pq.add(new int[]{'a', a});
        if (b > 0) pq.add(new int[]{'b', b});
        if (c > 0) pq.add(new int[]{'c', c});

        StringBuilder res = new StringBuilder();

        while (!pq.isEmpty()) {

            int[] first = pq.poll();

            int len = res.length();
            if (len >= 2 && res.charAt(len - 1) == first[0] && res.charAt(len - 2) == first[0]) {

                if (pq.isEmpty()) break;

                int[] second = pq.poll();
                res.append((char) second[0]);
                second[1]--;

                if (second[1] > 0) pq.add(second);

                pq.add(first);
            }
            else {
                res.append((char) first[0]);
                first[1]--;

                if (first[1] > 0) pq.add(first);
            }
        }

        return res.toString();
    }
}