Minimax algorithm developed for Connect4
You can play around with Connect4 here
My algorithm's maximum workable depth is 7 due to the computation limit. The algorithm is based on Minimax, which finds the scores for each possible step (1st~7th column in this game) The winning rate of this algorithm is nearly 93%, compared to the best strategy (with depth = 9) I got first ranking with this in the tournament of best_move functions in my Intro to C Programming course.
The result can be seen here (My competition ID is ee15flp).