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?
Input: n = 2
Output: 2
Explanation: There are two ways to climb to the top:
1. 1 step + 1 step
2. 2 steps
Input: n = 3
Output: 3
Explanation: There are three ways to climb to the top:
1. 1 step + 1 step + 1 step
2. 1 step + 2 steps
3. 2 steps + 1 step
1 ≤ n ≤ 45To reach step n, you can climb either from step n-1 or step n-2.
Don't think about the first move. Think about the last one.
Time O(n)Space O(1)
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