TY - GEN

T1 - Minimum cost partitions of trees with supply and demand

AU - Ito, Takehiro

AU - Hara, Takuya

AU - Zhou, Xiao

AU - Nishizeki, Takao

PY - 2010

Y1 - 2010

N2 - Let T be a given tree. Each vertex of T is either a supply vertex or a demand vertex, and is assigned a positive integer, called the supply or the demand. Every demand vertex v of T must be supplied an amount of "power," equal to the demand of v, from exactly one supply vertex through edges in T. Each edge e of T has a direction, and is assigned a positive integer which represents the cost required to delete e from T or reverse the direction of e. Then one wishes to obtain subtrees of T by deleting edges and reversing the directions of edges so that (a) each subtree contains exactly one supply vertex whose supply is no less than the sum of all demands in the subtree and (b) each subtree is rooted at the supply vertex in a sense that every edge is directed away from the root. We wish to minimize the total cost to obtain such rooted subtrees from T. In the paper, we first show that this minimization problem is NP-hard, and then give a pseudo-polynomial-time algorithm to solve the problem. We finally give a fully polynomial-time approximation scheme (FPTAS) for the problem.

AB - Let T be a given tree. Each vertex of T is either a supply vertex or a demand vertex, and is assigned a positive integer, called the supply or the demand. Every demand vertex v of T must be supplied an amount of "power," equal to the demand of v, from exactly one supply vertex through edges in T. Each edge e of T has a direction, and is assigned a positive integer which represents the cost required to delete e from T or reverse the direction of e. Then one wishes to obtain subtrees of T by deleting edges and reversing the directions of edges so that (a) each subtree contains exactly one supply vertex whose supply is no less than the sum of all demands in the subtree and (b) each subtree is rooted at the supply vertex in a sense that every edge is directed away from the root. We wish to minimize the total cost to obtain such rooted subtrees from T. In the paper, we first show that this minimization problem is NP-hard, and then give a pseudo-polynomial-time algorithm to solve the problem. We finally give a fully polynomial-time approximation scheme (FPTAS) for the problem.

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U2 - 10.1007/978-3-642-17514-5_30

DO - 10.1007/978-3-642-17514-5_30

M3 - Conference contribution

AN - SCOPUS:78650875983

SN - 3642175163

SN - 9783642175169

T3 - Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

SP - 351

EP - 362

BT - Algorithms and Computation - 21st International Symposium, ISAAC 2010, Proceedings

T2 - 21st Annual International Symposium on Algorithms and Computations, ISAAC 2010

Y2 - 15 December 2010 through 17 December 2010

ER -