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。...

Little Leon lives in the forest. He has recently noticed that some trees near his favourite path are withering, while the other ones are overhydrated so he decided to learn how to control the level of the soil moisture to save the trees.There are nn trees