The contents of the first three chapters are not particularly difficult. They are almost all basic concepts. The fourth chapter of this book is called "Induction, Recursion and Simplification" , this is one of the earlier algorithmic ideas we are exposed to. Let’s first explain some of these three concepts:
1. The reduction method refers to transforming a certain problem into another problem. Generally speaking, we Tend to transform a more difficult unknown problem into a simpler known problem to solve. (Simplify the problem)
2. The induction method is used to prove whether a certain statement is true for reading a certain large object class. We must first prove that it is true under a certain basic situation, and then prove that it can be passed through a The object is communicated to the "next" object. (The mathematical induction method encountered in high school and the induction method in advanced mathematics are similar to this)
3. The recursive method is mainly used for self-calling of functions. For example, "There is nothing more terrifying in the world than terror itself", or "Big fish eat small fish, and small fish eat shrimps."
First let’s talk about an example of reduction method.
-We want to find two numbers from a list of numbers that are closest to each other but not identical (the absolute difference between the two numbers is the smallest).
The simplest idea is that we can use a double loop to subtract numbers one by one, and then take the absolute value and compare it with the current minimum each time. Finally, we can definitely find the two numbers we want, code As follows:
We can analyze this problem. The two numbers we are looking for with the smallest absolute value difference must be two adjacent numbers on the one-dimensional number axis. number, then we only need to subtract two adjacent numbers.
Generally speaking, if you have no programming foundation, it is not recommended to use this book as an introductory tutorial. If you have the basics, it is a good choice to use it as an improvement material.
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