South Korean professional Go player Lee Sedol (C) attends a press conference after finishing the final match of the Google DeepMind Challenge Match against Google's artificial intelligence program, AlphaGo. [Photo/Xinhua]

After his first win on Sunday, Lee offered to play black stones, with which he believed AlphaGo displayed a relatively weak play.

About two and a half hours into the match, a tight game continued. AlphaGo attacked the right center by seeking to build a large territory there, while Lee built a territory in the lower-right side of the board according to his strategy which reportedly occupies more areas in an early phase.

In the fourth match where Lee won his first victory after three straight losses, AlphaGo made bad moves after Lee began to dominate in building a territory.