hdu 2121 , hdu 4009 无定根最小树形图 hdu 2121 题目:给出m条有向路,根不确定,求一棵最小的有向生成树。 分析:增加一个虚拟节点,连向n个节点,费用为inf(至少比sigma(cost_edge)大)。以该虚拟节点为根求一遍最小树形图算法,这时肯定存在解,如果费用>=inf时,说明无解。这是因为sigma(cost_edge)<inf。
1:构造虚根最小树形图 因为是不定根,所以我们可以假设一个虚拟根,分别与n个点都有一条权值为r的虚边,假如我们把r设的非常大的话,我们求出来的最小数形图去掉虚点和虚边就是最小树形图了,如果去掉虚点和虚边图形变得不连通了,那么说明这n个点不存在最小树形图,因为r非常大,并且不存在任何一条边替换掉r...
hdu2121无定根的最小树形图 无定根的最小树形图,像网络流的超级源和超级汇一样加一个起点,用邻接表(n>1000) n<1000用邻接矩阵 #include#include<set>#include<ctime>#include<cmath>#include<queue>#include<stack>#include<vector>#include<cstdio>#include<iomanip>#include<cstdlib>#include<cstring>#include...
无定根的最小树形图,像网络流的超级源和超级汇一样加一个起点,用邻接表(n>1000) n<1000用邻接矩阵 View Code
After awarded lands to ACMers, the queen want to choose a city be her capital. This is an important event in ice_cream world, and it also a very difficult problem, because the world have N cities and M roads, every road was directed. Wiskey is a chief engineer in ice_cream world. ...