There is a stair of 10 steps.IF you can only go up for 1 steps or 2 steps once.How many ways canyou use to get to the 10th step?

There is a stair of 10 steps.IF you can only go up for 1 steps or 2 steps once.How many ways canyou use to get to the 10th step?
There is a stair of 10 steps.IF you can only go up for 1 steps or 2 steps once.How many ways can
you use to get to the 10th step?

There is a stair of 10 steps.IF you can only go up for 1 steps or 2 steps once.How many ways canyou use to get to the 10th step?
10级台阶可以分成:
10个1级;
8个1级,1个2级;
6个1级,2个2级;
4个1级,3个2级;
2个1级,4个2级;
5个2级
共6种分台阶的办法,
然后排列组合,
共有,1+9C1+(7C2+7C1)+(5C3+5C2+5C1)+(5C2+5C1)+1=79 种上楼的方法

five