LeetCode-70. Climbing Stairs

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问题描述

You are climbing a staircase. It takes n steps to reach the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

Example :

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Input: n = 2
Output: 2
Explanation: There are two ways to climb to the top.
1. 1 step + 1 step
2. 2 steps

解答

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/*
 * @Description: 70. Climbing Stairs
 * @Author: libk
 * @Github: https://github.com/libk
 */
/**
 * @param {number} n
 * @return {number}
 */
const climbStairs1 = function (n) {
  let res = 1
  let pre = 1
  let preOfPre = 1

  for (let i = 2; i <= n; i++) {
    res = pre + preOfPre
    preOfPre = pre
    pre = res
  }
  return res
}