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2020-2021:teams:looking_up_at_the_starry_sky:shenzhonghai:dsu_on_tree

MAIN

主要依据轻重链思想，暴力统计轻儿子对当前节点答案贡献，先递归解决轻儿子并消除影响，再递归重儿子并保留影响用于此节点统计答案。

全局时间复杂度 $O(n\log n)$