write a brute force solution which gives correct answer and test your current solution by generation random numbers using generator and find the test case where your solution result in wrong answer

As a software engineer, I apply engineer-like strategies.

1 . Write readable code to make logic clear and minimize bugs

• use lambda functions for logic repeated more than twice.
• assign calculation results to variables to clarify their meaning
• give variables short but descriptive names

2 . Print debugging -> cpp-dump

Understand what each section is doing. Then Just check line by line. Think about whether it's reasonable carefully. Pay special attention to the interaction between operations.

In addition, you can write down error-prone things before you write code.

You can read um_nik's blog. I think it's meticulous and useful.