The normalization method of permutation refers to treating all permutations and combinations as isomorphism (isomorphism refers to two examples with the same structure but different arrangement of elements), that is to say, we no longer need to calculate each specific permutation and combination, but only need to calculate the number of permutations and combinations under isomorphism. For example, three different letters, A, B and C, have six permutations and combinations, but because they are all three-element permutations, their isomorphism number is only 1, which is 3! =6。

The normalization method of permutation has been widely used in many mathematical problems. In combinatorial mathematics, the normalization method of permutation can greatly simplify the problem, especially when calculating combinatorial problems. In the design of computer science algorithm, the normalization of permutation is also widely used. For example, in many search algorithms, normalization of permutation can help us to remove redundant search operations and reduce the amount of calculation.

The idea of arrangement standardization can be extended to a wider range of problems. For example, in the network, we can regard subgraphs with the same structure as isomorphism, thus simplifying the calculation of some network problems. Similarly, in chemical reactions and biology, the normalization method of permutation can be used to simplify some complex problems. It can be said that the normalization of permutation is a very common and important mathematical tool.