题目链接：ZOJ 1406 POJ 1251 Jungle Roads 丛林中的道路
Jungle Roads
Time Limit: 2 Seconds Memory Limit: 65536 KB
The Head Elder of the trZ??http://www.2cto.com/kf/ware/vc/" target="_blank" class="keylink">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