You are climbing a stair case. It takesnsteps 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?

Note:Givennwill be a positive integer.

Example 1:

Input:
 2

Output:
  2

Explanation:
  There are two ways to climb to the top.

1. 1 step + 1 step
2. 2 steps

Example 2:

Input:
 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

tag: DP

class Solution {
    public int climbStairs(int n) {
        if (n == 0 || n == 1) return 1;
        int[] dp = new int[n + 1];

        dp[0] = 1;
        dp[1] = 1;

        for (int i = 2; i <= n; i++){
            dp[i] = dp[i - 1] + dp[i - 2];
        }

        return dp[n];
    }
}