双语畅销书《艾伦图灵传》第5章:解谜接力赛(120)
Reducing the figure of thirty to a mere two for the sake of a diagram, the player (White) making a three-move look-ahead is confronted by a 'tree' such as:
Current position, W to play
当前局面，白方走棋Position resulting from the 2 possible W moves
白方的2种着法会导致的局面
Position resulting from the possible replies
黑方的着法会导致的局面Position resulting from the possible W replies.
白方的着法会导致的局面These positions are evaluated by scoring.
对这些局面用分数进行评估A human playing White might reason that it would be good to reach position E, but Black will not be so obliging, and will respond to move B by reply F.
白方可能会认为，到达E是最理想的，但黑方不会这么乐于助人，如果白方走到B，那么他就会回应F。A second best, for White, would be position D, but again it must be assumed that Black will play C to prevent this.
对白方而言，第二好的选择是D，但同样可以想见，黑方会走到C来避免D。Of the two evils, positions C and F, C is the lesser one, since at least it guarantees for White a position of value 27. So White plays move A.
在这两个不幸中，C和F局面相比，C的危险性更小一些，因为它能使白方保证至少达到价值为27的局面。因此白方会进行A移动。A 'machine' could simulate this train of thought by a method of 'backing up' the tree.
机器可以通过推导这棵树，来模拟这一系列想法。Having worked out all the scores for three moves ahead, it would then label the intermediate positions on a minimax basis.
对三步之后的各种局面进行评估之后，根据最大值最小化的思想，对中间各层的局面进行标示。It would assign 27 to C, 45 to D, 81 to E, 16 to F (the best in each case), then 27 to A, 16 to B (the worst in each case), and finally select move A for White.
它会将C标为27, D标为45, E标为81, F标为16（每个下面的最好局面），然后将A标为27, B标为16（每个下面的最坏局面）。
