We use induction. Suppose it is true for any number < N.
Pick a point P inside the polygon formed by the points so that no two points in the original sets are colinear with P. Draw a line thru P, and rotate the line, to a place where there are equal numbers of blue and red points on each side of the line. By the inductive assumption we can do it for each side.
哈哈哈哈 O(∩_∩)O哈哈~ 好久不来了，不小心看了一眼自己主页，发现自动关联了自己以往发过的帖，点进这个看了一眼，笑个半死。。。敢情我当初还发过这么搞笑的东西啊，我自己完全不记得了 
雷达卡
发表于 2005-4-8 02:18:32
