��</th>
            </tr>
            <tr>
                <td class="symbol"><img src="formula_select.svg"/></td>
                <td>比较秩</td>
                <td class="code">rank[x] &gt; rank[y]:</td>
            </tr>
            <tr>
                <td class="symbol"><img src="formula_update_rank.svg"/></td>
                <td>将秩加 1</td>
                <td class="code">rank[y]++</td>
            </tr>
            <tr>
                <td class="symbol"><img src="formula_update.svg"/></td