lessons/课程/插图/09-基环树/00-基环树-01-多一条边.svg

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  <title id="title">树加一条边形成基环树</title><desc id="desc">灰色边是一棵树，红色额外边和树路径形成唯一环。</desc>
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  <text x="27" y="31" class="note">先有一棵树；红色额外边把它两端的唯一树路径闭成一圈。</text><line class="tree" x1="170" y1="160" x2="335" y2="80"/><line class="tree" x1="335" y1="80" x2="510" y2="155"/><line class="tree" x1="510" y1="155" x2="680" y2="85"/><line class="tree" x1="510" y1="155" x2="625" y2="235"/><line class="extra" x1="170" y1="160" x2="510" y2="155"/><circle class="node" cx="170" cy="160" r="26"/><circle class="node" cx="335" cy="80" r="26"/><circle class="node" cx="510" cy="155" r="26"/><circle class="node" cx="680" cy="85" r="26"/><circle class="node" cx="625" cy="235" r="26"/><text class="label" x="161" y="169">A</text><text class="label" x="326" y="89">B</text><text class="label" x="501" y="164">C</text><text class="label" x="671" y="94">D</text><text class="label" x="616" y="244">E</text><text x="260" y="210" style="font-family:system-ui,sans-serif;font-size:20px;fill:#dc2626">额外边</text>
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