2017 USAMO Problems/Problem 2: Difference between revisions
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==Problem== | |||
Let <math>m_1,\dotsc,m_n</math> be a collection of <math>n</math> positive integers, not necessarily distinct. For any sequence of integers <math>A = (a_1,\dotsc,a_n)</math> and any permutation <math>w_1,\dotsc,w_n</math> of <math>m_1,\dotsc,m_n</math>, define an <math>A-inversion</math> of <math>w</math> to be a pair of entries <math>w_i,w_j</math> with <math>i<j</math> for which one of the following condition holds: | |||
Revision as of 21:08, 27 November 2017
Problem
Let 
be a collection of 
positive integers, not necessarily distinct. For any sequence of integers 
and any permutation 
of , define an 
of 
to be a pair of entries 
with 
for which one of the following condition holds:
