 Many-one reduction

A many-one reduction $A{\le }_{m}B$ is a total computable $f$ satisfying $x\in A$ exactly when $f(x)\in B$.

Many-one reduction, also known as **mapping reduction**, is a concept in computational complexity theory used to compare the difficulty of decision problems. It involves transforming instances of one decision problem into instances of another decision problem in such a way that the answer to the original problem can be easily derived from the answer to the transformed problem.