Combinatorial mathematics Chapter 1 Notes

Concept

Combinatorial mathematics is also called combinatorial theory , This paper mainly studies the problem of permutation and combination in discrete mathematics , Study counting techniques , And prove its existence and calculate the quantity .

magic square

The earliest combinatorial mathematics in history , Its characteristic is that any one >=3 Of n, There is the case that the sum of the numbers in each row and column is equal , This sum is called magic sum .

Magic square construction method

First put... In the middle of the first line 1, Then, according to the circular rule, put a number at the top right of the previous grid , When coincident, it is placed directly below the previous number .

Seven bridge problem

notes ： An odd number of points can only be the beginning and the end , Otherwise, you can't finish it in one stroke .