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计数是组合数学的重要内容,计数的方法有分类法、分步法、递推法和对应法等.1.分类计数.在计数时,为了做到不重复也不遗漏,可以先将图形按某个标准分类,然后将其每一类的方法数相加,便得到了总数.这种方法叫做分类法.2.分步计数.在计数时,为了有序地思维,我们常将其分成若干步,然后将其每一步的方法数相乘,便得到了总数.这种方法叫做分步法.
Counting is an important part of combinatorial mathematics. Counting methods include taxonomy, step-by-step, recursive, and correspondence methods. 1. Sorting Counting. When counting, you can press the graph first in order not to repeat or omit it. A standard classification, and then add the number of methods of each type, to get the total number. This method is called the classification method. 2. Counting step by step. In order to count, in order to order thinking, we often divide it into A number of steps are then multiplied by the number of methods for each step to obtain the total number. This method is called step-by-step.