Viiisit [LeetCode] - 70. Climbing Stairs

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Problem - Climbing Stairs

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?

翻譯蒟蒻

一次只能爬一階或兩階，求出最多有幾種可以爬到最高的方法

---

• Example 1:

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

• Example 2:

  Input: n = 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

---

Solution - JavaScript

/**
 * @param {number} n
 * @return {number}
 */
var climbStairs = function(n) {
  let arr = [0, 1, 2];
  if (n < 3) {
    return arr[n];
  }

  for (let i = 3; i <= n; i++) {
    arr[i] = arr[i - 1] + arr[i - 2];
  }

  return arr[n];
};

Solution - Ruby

def climb_stairs(n)
  arr = [0, 1, 2]

  return arr[n] if n < 3

  (3..n).each do |i|
      arr[i] = arr[i-1] + arr[i-2]
  end
  
  return arr[n]
end

Solution - PHP

function climbStairs($n) {
  $arr = [0, 1, 2];

  if ($n < 3) {
      return $arr[$n];
  };

  for ($i = 3; $i <= $n; $i++) {
      $arr[$i] = $arr[$i-1] + $arr[$i-2];
  };

  return $arr[$n];
}

LeetCode 傳送門 - Climbing Stairs