LeetCode.ClimbStairs.Fibbonacci

task

Here we can recognize fibbonacci sequence

recursievely

public class Solution {
    public int ClimbStairs(int n) {

       if (n == 0)
         return 1;
  
       return n > 1 ? ClimbStairs(n - 1) + ClimbStairs(n -2) : n; 
    }
}

iteratievely

public class Solution {
    public int ClimbStairs(int n) {

        if (n <= 1)
          return 1;

        int first = 1;
        int second = 1;          

        for (int i = 2; i <= n; i++) { 
          int sum = first + second;
          first = second;
          second = sum;   
        }

        return second;
    }
}