I did competitive programming from 2018 to 2021 and went to the USACO training camp in 2020 and 2021. Here are some of the worst programs I ever wrote, for your viewing pleasure.
USACO Guide: A free, high quality guide for USACO
Library: Clean templates and algorithm implementations that I use
USACO: Clean USACO solutions
USACO Camp: Miscellaneous USACO Camp solutions
IOI: IOI solutions
Google Code Jam: Google Code Jam solutions
ACSL: ACSL code and resources
Idiot Code-Golf: Really stupid code competition
LCS Resources: Ladue Computer Science resources for competitive programming
Log: Log of solved problems and notes