Classical algorithm (13) n positive integers randomly generated and as s--projection method

There are many solutions to n positive integers that are randomly generated and are s. Here is a more efficient and more interesting solution-projection method.

Taking the 4 numbers of generation and 20 as an example, we can first generate the random generation of three digits between 0 and 20, and assume the 4,7,18. Then draw the three numbers on the X-y axis, as shown below:

The values are then projected onto the y-axis, which is shown below:

It is easy to see from the diagram Ab,bc,cd, de these four paragraphs of length and certainly 20. Thus the length of the four paragraphs of Ab,bc,cd,de is 20 of the 4 numbers, the 4 numbers are 4,3,11, 2 respectively.