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?

**Note:** Given *n* will be a positive integer.

**Example 1:**

Input:2Output:2Explanation:There are two ways to climb to the top. 1. 1 step + 1 step 2. 2 steps

**Example 2:**

Input:3Output:3Explanation: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

## Solution

n = 5

int[] dp = new int[n+1];

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

dp[2] = dp[0] + dp[1] = 2;

dp[3] = dp[2] + dp[1] = 2 + 1 = 3;

dp[4] = dp[3] + dp[2] = 3 + 2 = 5;

dp[5] = dp[4] + dp[3] = 5 + 3 = 8;

### Code

public class Solution { public int ClimbStairs(int n) { //Edge Case if(n < 2) 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]; } }