Mathematics for Informatics and Computer Science How many ways do exist to mix different ingredients, how many chances to win a gambling game, how many possible paths going from one place to another in a network? To this kind of questions Mathematics applied to computer gives a stimulating and exhaustive answer. This text, presented in three parts (Combinatorics, Probability, Graphs) addresses all those who wish to acquire basic or advanced knowledge in combinatorial theories. It is actually also used as a textbook. Basic and advanced theoretical elements are presented through simple applications like the Sudoku game, search engine algorithm and other easy to grasp applications. Through the progression from simple to complex, the teacher acquires knowledge of the state of the art of combinatorial theory. The non conventional simultaneous presentation of algorithms, programs and theory permits a  powerful mixture of theory and practice. All in all, the originality of this approach gives a refreshing view on combinatorial theory.