1.？ Adjacent problem binding method:

The title stipulates that several adjacent elements are bound into a group and arranged into a large element.

2.？ Interpolation method for phase separation problem;

To solve the problem of element separation (that is, non-adjacency), all elements without position requirements can be arranged first, and then the specified separated elements can be inserted into the gaps and both ends of the above elements.

3.？ Simplified method of sequencing problem;

In the arrangement problem, some elements must be limited to a certain order, and the method of reducing multiples can be used.

4.？ Step-by-step algorithm for label sorting problem;

Arranging elements in a specified position can be done by arranging one element first, then arranging another element in the second step, and so on.

5.？ Fractional method for ordered distribution problems;

Orderly allocation problem refers to dividing elements into several groups, which can be grouped step by step.

In this way, people still attribute a combinatorial problem to an algebraic or analytical problem (correspondence and estimation), just like facing geometry. In this way, many extremely complicated combination details can be ignored.

Complexity is a difficulty faced by human beings rather than individuals (such as cancer, weather forecast, etc.) ), but the Olympic proposition examines personal ability, so the proposer can try to avoid the complexity of combination.

In other words, the combinatorial problem must be solved by global correspondence, algebraic reduction or local treatment. If you encounter a very difficult problem and don't have a clue when you do it, you must be caught in the complexity of the combination details, but you didn't think of or find the first few methods.