Longest Happy String
<p>A string <code>s</code> is called <strong>happy</strong> if it satisfies the following conditions:</p>

<ul>
	<li><code>s</code> only contains the letters <code>&#39;a&#39;</code>, <code>&#39;b&#39;</code>, and <code>&#39;c&#39;</code>.</li>
	<li><code>s</code> does not contain any of <code>&quot;aaa&quot;</code>, <code>&quot;bbb&quot;</code>, or <code>&quot;ccc&quot;</code> as a substring.</li>
	<li><code>s</code> contains <strong>at most</strong> <code>a</code> occurrences of the letter <code>&#39;a&#39;</code>.</li>
	<li><code>s</code> contains <strong>at most</strong> <code>b</code> occurrences of the letter <code>&#39;b&#39;</code>.</li>
	<li><code>s</code> contains <strong>at most</strong> <code>c</code> occurrences of the letter <code>&#39;c&#39;</code>.</li>
</ul>

<p>Given three integers <code>a</code>, <code>b</code>, and <code>c</code>, return <em>the <strong>longest possible happy </strong>string</em>. If there are multiple longest happy strings, return <em>any of them</em>. If there is no such string, return <em>the empty string </em><code>&quot;&quot;</code>.</p>

<p>A <strong>substring</strong> is a contiguous sequence of characters within a string.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> a = 1, b = 1, c = 7
<strong>Output:</strong> &quot;ccaccbcc&quot;
<strong>Explanation:</strong> &quot;ccbccacc&quot; would also be a correct answer.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> a = 7, b = 1, c = 0
<strong>Output:</strong> &quot;aabaa&quot;
<strong>Explanation:</strong> It is the only correct answer in this case.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>0 &lt;= a, b, c &lt;= 100</code></li>
	<li><code>a + b + c &gt; 0</code></li>
</ul>
Greedy; String; Heap (Priority Queue)
class Solution {
    public String longestDiverseString(int a, int b, int c) {
        Queue<int[]> pq = new PriorityQueue<>((x, y) -> y[1] - x[1]);
        if (a > 0) {
            pq.offer(new int[] {'a', a});
        }
        if (b > 0) {
            pq.offer(new int[] {'b', b});
        }
        if (c > 0) {
            pq.offer(new int[] {'c', c});
        }

        StringBuilder sb = new StringBuilder();
        while (pq.size() > 0) {
            int[] cur = pq.poll();
            int n = sb.length();
            if (n >= 2 && sb.codePointAt(n - 1) == cur[0] && sb.codePointAt(n - 2) == cur[0]) {
                if (pq.size() == 0) {
                    break;
                }
                int[] next = pq.poll();
                sb.append((char) next[0]);
                if (next[1] > 1) {
                    next[1]--;
                    pq.offer(next);
                }
                pq.offer(cur);
            } else {
                sb.append((char) cur[0]);
                if (cur[1] > 1) {
                    cur[1]--;
                    pq.offer(cur);
                }
            }
        }

        return sb.toString();
    }
}