Hi, in some problems an acquaintance solves some problems from the ICPC by associating a matrix to certain values of a function and then he obtains the final answer after taking the exponential of the matrix to some power and looking at some value of the matrix (e.g. A[0][0] or A[1][n] or something).

May someone give me a reference for this? what’s the name of this technique? Sorry for not being more accurate but it’s all I know/understand. Thanks in advance.