Abstract

A matroid M is an ordered pair (E,I), where E is a finite set called the ground set and a collection I⊂2E called the independent sets which satisfy the conditions: (I1) ∅∈I, (I2) I′⊂I∈I implies I′∈I, and (I3) I1,I2∈I and |I1|<|I2| implies that there is an e∈I2 such that I1∪{e}∈I.
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