回复：奥数题：怎样画21根直线和118个交点

来源: 于 2009-03-26 12:22:11 [博客] [旧帖] [给我悄悄话] 本文已被阅读：次

10x10 grid give 100交点

find 1交点on two opposite edges. draw the last line through these 2交点. Make sure not hit any other 交点 or simply pick up 2 corner points of biggest rectangle that is made by two adjacent parallel lines.