MathDB
subset partition

Source: Serbia 2003

April 28, 2008
inductionconicsellipsevectorcombinatorics proposedcombinatorics

Problem Statement

Let n n be an even number, and S S be the set of all arrays of length n n whose elements are from the set {0,1} \left\{0,1\right\}. Prove that S S can be partitioned into disjoint three-element subsets such that for each three arrays \left(a_i\right)_{i \equal{} 1}^n, \left(b_i\right)_{i \equal{} 1}^n, \left(c_i\right)_{i \equal{} 1}^n which belong to the same subset and for each i∈{1,2,...,n} i\in\left\{1,2,...,n\right\}, the number a_i \plus{} b_i \plus{} c_i is divisible by 2 2.