
ZOJ Problem Set  2134
A university network is composed of N computers. System administrators gathered information on the traffic between nodes, and carefully divided the network into two subnetworks in order to minimize traffic between parts. A disgruntled computer science student Vasya, after being expelled from the university, decided to have his revenge. He hacked into the university network and decided to reassign computers to maximize the traffic between two subnetworks. Unfortunately, he found that calculating such worst subdivision is one of those problems he, being a student, failed to solve. So he asks you, a more successful CS student, to help him. The traffic data are given in the form of matrix C, where Cij is the amount of data sent between ith and jth nodes (Cij = Cji, Cii = 0). The goal is to divide the network nodes into the two disjointed subsets A and B so as to maximize the sum {Cij} for all i belongs to A and j belongs to B.
The first line of input contains a number of nodes N (2 <= N <= 20). The following N lines, containing N spaceseparated integers each, represent the traffic matrix C (0 <= Cij <= 10000).
Output must contain a single integer  the maximum traffic between the subnetworks.
The first line of a multiple input is an integer N, then a blank line followed by N input blocks. Each input block is in the format indicated in the problem description. There is a blank line between input blocks. The output format consists of N output blocks. There is a blank line between output blocks.
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90 Source: Northeastern Europe 2002, FarEastern Subregion 