How are this type of cheaters caught?

#	User	Rating
1	tourist	3947
2	jiangly	3734
3	Radewoosh	3646
4	jqdai0815	3620
4	Benq	3620
6	orzdevinwang	3612
7	ecnerwala	3581
8	Geothermal	3569
8	cnnfls_csy	3569
10	ksun48	3479

#	User	Contrib.
1	awoo	162
2	maomao90	160
3	nor	157
4	atcoder_official	156
4	cry	156
6	adamant	155
6	-is-this-fft-	155
8	maroonrk	154
9	Petr	146
10	djm03178	145

If I am a cheater and have solutions to some problems, and for each solution, I read the code, understand it, and then write my own code from scratch based on the idea of the code I copied as if I came up with the idea myself, how can Codeforces catch me? How can the Codeforces system detect this type of cheating?

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