First, the basic idea
When a problem is more complicated, by decomposition or conversion , to convert it into a series of simpler sub-problems, and then achieved by solving the original problem solving these subproblems. Reduction problem solving process is actually a tree generation solution that prove the original node is solvable process node.
(1) decomposition
( "And" P equivalent to the original problem is decomposed sub-problems obtained.)
If a problem P can be grouped around a set of sub-problems P1, P2, ..., Pn, and the original problem P only solution only when all the sub-issues Pi has a solution to any problem a child Pi no solution will lead to the original problem P no solution, called decomposition problem go about this.
(2) the equivalent transformation
( "Or" equivalent to the original problem P transform, i.e. sub-problems obtained.)
If a problem P can be grouped around a set of sub-problems P1, P2, ..., Pn, Pi and sub-problems as long as there is a solvable problem P have the original solution only when all the sub-issues Pi are no solution of the original problem P was no solution, saying that such a return is approximately equivalent transformation issues, referred to as transformation.
Second, the problem of reduction and / or tree representation
Third, the statute examples
