Climbing Stairs

import { range } from '@algorithm/lib';
 
export function climbStairs(n: number): number {
  if (n <= 2) {
    return n;
  }
  const dp = new Array<number>(n + 1).fill(0);
  dp[1] = 1;
  dp[2] = 2;
  for (const i of range(3, n + 1)) {
    dp[i] = dp[i - 1] + dp[i - 2];
  }
  return dp[n];
}