s0070_climbing_stairs

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. 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

Solution

func climbStairs(n int) int {
	f := make([]int, n+1)
	f[0] = 1
	f[1] = 2
	if n > 2 {
		for i := 2; i < n; i++ {
			f[i] = f[i-1] + f[i-2]
		}
	}
	return f[n-1]
}