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Connect Four (also known as Captain's Mistress, Four Up, Plot Four, Find Four, Fourplay, Four in a Row and Four in a Line) is a two-player connection game in which the players first choose a color and then take turns dropping colored discs from the top into a seven-column, six-row vertically suspended grid. The pieces fall straight down, occupying the next available space within the column. The objective of the game is to connect four of one's own discs of the same color next to each other vertically, horizontally, or diagonally before your opponent. Connect Four is a strongly solved game. The first player can always win by playing the right moves. The game was first sold under the famous ''Connect Four'' trademark by Milton Bradley in February 1974. ==Mathematical solution== Connect Four is a two-player game with "perfect information." This term describes games where one player at a time plays, players have all the information about moves that have taken place, and all moves that can take place, for a given game state. Connect Four also belongs to the classification of an adversarial, zero-sum game, since a player's advantage is an opponent's disadvantage. One measure of complexity of the Connect Four game is the number of possible games board positions. For classic Connect Four played on 6 high, 7 wide, grid, there are 4,531,985,219,092 positions〔(''Number of legal 7 X 6 Connect-Four positions after n plies'' ), Online Encyclopedia of Integer Sequences〕 for all game boards populated with 0 to 42 pieces. The game was first solved by James Dow Allen (October 1, 1988), and independently by Victor Allis (October 16, 1988).〔(【引用サイトリンク】title=John's Connect Four Playground )〕 Allis describes a knowledge based approach,〔Allis, Victor, (''A Knowledge-based Approach of Connect-Four'' ), Vrije Universiteit, October 1988〕 with nine strategies, as a solution for Connect Four. Allen also describes winning strategies〔 Allen, James D., (''Expert Play in Connect-Four'' ), 1990〕 in his analysis of the game. At the time of the initial solutions for Connect Four, brute force analysis was not deemed feasible given the game's complexity and the computer technology available at the time. Connect Four has since been solved with brute force methods beginning with John Tromp's work in compiling an 8-ply database〔〔Tromp, John, (''Connect-4 Data Set'' ), February 4, 1995〕 (Feb 4, 1995). The artificial intelligence algorithms able to strongly solve Connect Four are minimax or negamax, with optimizations that include alpha-beta pruning, dynamic history ordering of game player moves, and transposition tables. The code for solving Connect Four with these methods is also the basis for the Fhourstones integer performance benchmark. The solved conclusion for Connect Four is first player win. With perfect play, the first player can force a win,〔〔〔 on or before the 41st move〔asun.net, (''Four in a Row Solver'' ), August 2013〕 by starting in the middle column. The game is a theoretical draw when the first player starts in the columns adjacent to the center. For the edges of the game board, column 1 and 2 on left, and column 7 and 6 on right, the exact move-value score for first player start is loss on the 40th move,〔 and loss on the 42nd move,〔 respectively. In other words, by starting with the four outer columns, the first player allows the second player to force a win. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Connect Four」の詳細全文を読む スポンサード リンク
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