Past exam of the mathematics course of the University of Cambridge 2012 iii Paper 9 2 ii Solution Created 2026-10-03 Updated 2026-10-07
If some choice produced a graph with largest component of a graph smaller than , the balanced component cut result with packing parameter one would give an empty graph cut whose sides both have at least vertices. For any fixed such vertex set partition, a uniform edge of the complete graph crosses with probabilityTo avoid crossing in row , at least one of its offered edges must be noncrossing. The row's probability is . The rows consist of independent random variables, so at a union bound over at most vertex set partitions givesFor example, the positive integermakes this bound at most . Therefore every choice has a component of order at least , with probability tending to one. The simultaneous giant for fixed random-edge choice estimate includes choices made after seeing the entire array; it does not assume a particular online selection rule.