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. 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:

Solution

object Solution {
    def climbStairs(n: Int): Int = {
        if (n < 2) {
            return n
        }
        val cache = new Array[Int](n)

        // Initialize the cache for the first two steps
        cache(0) = 1
        cache(1) = 2

        // Fill in the cache using a loop
        for (i <- 2 until n) {
            cache(i) = cache(i - 1) + cache(i - 2)
        }

        cache(n - 1)
    }
}