摘要："BZOJ" 题意:给定一个$N$个点$M$条边的有向无环图,如果想要使得原图任意两点的连通性保持不变，最多能删掉多少条边?$Nv$的路径. 对于有向无环图,需要想到拓扑排序,算是一个看到有向无环图的思路之一. 拓扑排序时给每个节点$i$记录一个访问时间$num[i]=tim$,然后把每个节点的出边 阅读全文

摘要："BZOJ" 题意:给定一个大小为$n$的可重集合,求其所有子集的算术和的异或和.$n include include include include include include include include define ll long long using namespace std; b 阅读全文