text: // 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: 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
  
  
  
  class Solution {
  public:
      int climbStairs(int n) {
        if (n <= 2) { return n; }
        //return climbStairs(n-1) + climbStairs(n-2);
        vector<int> vec(n, 0);
        vec[0] = 1;
        vec[1] = 2;
        for (int i = 2; i < n; i++) {
          vec[i] = vec[i-1] + vec[i-2];
        }
        return vec.back();
      }
  };
  