leetcode-70 爬楼梯

/**
 * @param {number} n
 * @return {number}
 */
var climbStairs = function (n) {
  if (n === 1) return 1;
  if (n === 2) return 2;
  const dp = [1, 2];
  for (let i = 2; i < n; i++) {
    dp.push(dp[i - 1] + dp[i - 2]);
  }
  return dp.pop();
};

/**
 * @param {number} n
 * @return {number}
 */
var climbStairs = function (n) {
  if (n === 1) return 1;
  if (n === 2) return 2;
  const dp = [1, 2];
  for (let i = 2; i < n; i++) {
    // dp.push(dp[i - 1] + dp[i - 2]);
    const next = dp[0] + dp[1];
    dp[0] = dp[1]
    dp[1] = next;
  }
  return dp.pop();
};