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在进行立方和公式的推导前,首先,需要先了解三个有关于图形计数的知识点.一、“线段法”解决长方形网格计数问题对于解决长方形网格中包含的长方形数目之类的题目有很多方法,其中一种是“线段法”.我们知道在长方形网格中只要能够确定一条长方形的长和一条宽就可以确定一个长方形.对于n行n列的长方形网格,长边和宽边均由n条单元线段组成.利用枚举法可以知道对于长(宽),长度由1个单元线段组成的线段有n条,由2个单元线段组成的线段有n一1条,由3
First of all, we need to know three knowledge points about graph counting before we can derive cubes and formulas: “Line method ” Solve the problem of rectangular grid counting For solving the problem that the number of rectangles contained in rectangular grid and the like There are many ways to solve the problem, one of which is “Line Method ” We know that in rectangular grids, as long as you can determine the length and width of a rectangle to determine a rectangle. For n rows and n columns of rectangular grid, Long and wide by n unit line segment composition.Using the enumeration method can be known for the length (width), the length of the line segment composed of a unit n, the line segment composed of two unit n-1 By 3