3.20BJOI 第一次集训
T1: 一张 $n$ 个点 $m$ 条边的带权无向图,从 $m$ 条边中等概率随机选择一条将权值变为 $0$,求最小生成树权值和,$1\le n\le 10^5,1\le m\le 2\times10^5$
T2: 有四种物品,分别有 $n_1,n_2,n_3,n_4$ 个,求排成一排且任意两个相邻物品不同种的方案数,对 $10^9+7$ 取模,$0\le n...
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