algorithm

I want all the algorithm in C. The root directory is algo_c and the file name should be the name of the algorithm.

Start by inspecting the repository and the algo_c directory to determine which algorithms are already present and how they are organized. Define the initial algorithm scope, then place each C implementation in algo_c with a filename matching its algorithm; done means the agreed set is complete and consistently named.

Written by the indexing model from the issue text.