HDU 5047 Sawtooth（大数优化+递推公式） 来源：网络    编辑：admin http://acm.hdu.edu.cn/showproblem.php?pid=5047 题目大意：      给n条样子像“m”的折线，求它们能把二维平面分成的面最多是多少。 解题思路：     我们发现直线1条：2平面；2直线：4平面；3直线：7平面......因为

Problem Description Think about a plane: ● One straight line can divide a plane into two regions. ● Two lines can divide a plane into at most four regions. ● Three lines can divide a plane in