70. Climbing Stairs

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. 1 step + 1 step
2. 2 steps

Example 2:

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

Constraints:

• 1 <= n <= 45

# @lc code=start
using LeetCode

function climbing_stairs(n::Int)::Int
    n == 1 && return 1
    a, b = 1, 2
    for _ in 3:n
        a, b = b, a + b
    end
    return b
end

# @lc code=end

climbing_stairs (generic function with 1 method)

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