17. Climbing Stairs

Pattern: DP (Counting)

Problem

It takes n steps to reach the top. Each time you can climb 1 or 2 steps. How many distinct ways?

Solution

func climbStairs(n int) int {
    dp := make([]int, n+1)
    dp[1] = 1
    dp[2] = 2
    for i := 3; i <= n; i++ {
        dp[i] = dp[i-1] + dp[i-2]
    }
    return dp[n]
}

Essentially Fibonacci. O(n) time, O(n) space.