LeetCode-in-All
70. Climbing Stairs
Easy
You are climbing a staircase. It takes n steps to reach the top.
Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
Example 1:
Input: n = 2
Output: 2
Explanation: There are two ways to climb to the top.
-
1 step + 1 step
-
2 steps
Example 2:
Input: n = 3
Output: 3
Explanation: There are three ways to climb to the top.
-
1 step + 1 step + 1 step
-
1 step + 2 steps
-
2 steps + 1 step
Constraints:
1 <= n <= 45
Solution
-spec climb_stairs(N :: integer()) -> integer().
climb_stairs(N) ->
StairsRecursive = fun StairsRecursive(Res, Last, Curr) ->
if Curr == N ->
Res;
true ->
StairsRecursive(Res + Last, Res, Curr + 1)
end
end,
if N =< 2 ->
N;
true ->
StairsRecursive(2,1,2)
end.