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

I'm still a specialist and my level isn't that high.
But I'm a software engineer. So my strategy is engineer-like.

1 . Write readable code, which makes logic clear and easier to debug

• use lambda functions for logic repeated more than twice.
• use variables to clarify the meaning of calculation results
• 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.

Cout line by line is fast for me