Climbing Stairs

You are climbing a stair case. It takes n steps to reach to the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

Analysis: It's a DP problem. For each n, the last step can either climb 1 or 2 steps. So, f(n) = f(n-1) + f(n-2)

public class Solution {
    public int climbStairs(int n) {
        // the last step can climb either 1 or 2 steps, so ways = climbStairs(n-1) + climbStairs(n-2)
        if(n==0) return 0;
        else if(n == 1) return 1;
        
        int [] ways = new int[n+1];
        ways[1] = 1;
        ways[2] = 2;
        for(int i=3; i<ways.length; i++) {
            ways[i] = ways[i-1] + ways[i-2];
        }
        return ways[n];
    }
}