3.7.1. 3-dimensional-matching
Denotes the fact that, by reduction to 3 -dimensional -matching, deciding whether a constraint has a solution or not was shown to be NP -hard. The 3 -dimensional -matching problem can be described as follows: given a set , where , and are disjoint sets having the same number of elements , does contain a subset of elements such that no two elements of agree in any coordinate?