70. Climbing Stairs

class Solution {
public:
    int climbStairs(int n) {
      if(n==1)  return 1;

      int arr[46]={0};
      int cnt=3;
      arr[1]=1;
      arr[2]=2;
      
      for(int i=3;i<=n;i++)
      {
          arr[i]=arr[i-1]+arr[i-2];
          cnt++;
      }
      return arr[cnt-1];
    }
};