http://poj.org/problem?id=3494 http://zhuanlan.zhihu.com/qinchao/19873823 做法一：单调栈 http://poj.org/problem?id=2559 http://www.shuizilong.com/house/archives/ad-infinitum-math-programming-contest-september14 做法二：悬线法……