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vb le
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I think there are lot of similar problems. Here are two in vertex version and one in edge version:

  1. Does a given graph have an independent feedback vertex set? (we don't care about the size of the set). This problem is NP-complete; the proof can be derived from the proof of Theorem 2.1 in Garay et al..

  2. Does a given graph have a vertex cover that induces a tree? (we don't care about the size of the set). This paper gives an NP-completeness proof for this problem (Theorem 2); even for bipartite graphs.

  3. Does a given graph have a dominating edge set the edges of which form an induced $1$-regular subgraph? (also known as dominating induced matching or efficient edge dominating; the vertex version is given in the second answer by Mohammad. Again, we don't care about the size of the set). This problem is NP-complete (well-known), even for planar bipartite graphs.

vb le
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