Cloth的博客

有n片荷叶依次排在水面上，第i片荷叶能够到达第[i+1, i+ai]片荷叶上，由于这两只青蛙比较笨，所以在某片荷叶上时它们会随机选择下一片可达范围内的荷叶，在从1号荷叶出发到达n号荷叶的过程中，求这两只青蛙有多大的概率以相同步数到达n号荷叶，两青蛙运动是相互独立的。...

Painting is always a boring job.There are nnn blocks on an infinite two-dimensional plane. Each block is a rectangle parallel to the xxx-axis and yyy-axis with a non-zero area. The coordinates of bottom-left corner and top-right corner of the iii-th bl