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Let HALF-CLIQUE={<G>|Gs an undirected graph having a complete subgraph with at leastm/2 nodes, where m is the number of nodes inG. Show that HALF-CLIQUE is NP-complete.

Short Answer

Expert verified

The clique is ka clique of g, and hence⟨G,k⟩∈CLIQUE.

Step by step solution

01

Step 1:Undirected graph of the nodes

HALF-CLIQUE∈NP:

Let N be the nondeterministic polynomial time (NTM) that decides HALF-CLIQUEin polynomial time.

N can be described as follows:

N=''on input graph ⟨G⟩:

Non-deterministically choose at leastn/2 nodes

Verify whethern/2 nodes form a clique

If they form a clique then accept.

Otherwise, reject".

Therefore,HALF-CLIQUE∈NP

CLIQUE⩽pHALF-CLIQUE:

A reduction from $C L I Q U E$ to $H A L F-C L I Q U E$ as follows:

On input ⟨G,k⟩,where Gis a graph on n verifies and k is an integer:

02

Step 2:Size of the Half-Clique

When k<n/2G has a k-clique, then Ghas a clique of size.

k+n-2k=2n-2k/2

width="197">k+n-2k=2n-2k/2

Therefore, the HALF-CLIQUE is NP- complete.

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