📂
LeetCode Note
  • Introduction
  • Tools
    • Clean Code
    • 英文小辭典
    • JS Reference
    • 常見 Edge Case
    • Array Method
    • Object Method
    • Function
    • Hashing
    • Prototype
    • 處理 Array 小撇步
    • String Method
    • Math / Date
    • loop
    • JSON.xx / localStorage
    • Date
    • Regex
    • Memorization
    • reduce condition
    • 命名
  • 筆記 Note
    • Promise
    • Walking the DOM
    • Element size and scrolling
    • CSS
  • Leetcode todo
    • ToDo
  • Array
    • # Select random poker without duplicates
    • # 最少替換達成不連續字串
    • # 724 Find Pivot Index
    • # 747. Largest Number At Least Twice of Others
    • # 01 getMaxProfit
    • # maxOfBiggestVal
    • # findSecondLargest
    • # 41 First Missing Positive
    • # 134 Gas Station (有圖)
    • # 202 Happy Number
    • # 344 Reverse String
    • # 412 Fizz Buzz
    • # 561 Array Partition I
    • # 804 Unique Morse Code Words
    • # 905 Sort Array By Parity
    • # 121. Best Time to Buy and Sell Stock.js
    • # 122 Best Time to Buy and Sell Stock II
    • # 189 Rotate Array
    • # 229 Majority Element II
    • # 268 Missing Number.
    • # 299 Bulls and Cows (有圖)
    • # 896 Monotonic Array
    • # 1002 Find Common Characters
    • # 1051 Height Checker
    • # 1185 Day of the Week
    • # 169 Majority Element
    • # 605. Can Place Flowers
    • # 350 Intersection of Two Arrays II (有圖)
    • # 482. License Key Formatting
  • Set / Map
    • # GetLengthOfLongestSubstring
    • #1 Two Sum
    • # 217 Contains Duplicate
    • # 1122 Relative Sort Array
    • # 1160 Find Words That Can Be Formed by Characters
    • #811 Subdomain Visit Count
    • # 349 Intersection of Two Arrays
    • # 819 Most Common Word
  • Two Pointer
    • #704. Binary Search
    • #26 Remove Duplicates from Sorted Array (有圖)
    • #27 Remove Element
    • # 66 Plus One
    • # 80 Remove Duplicates from Sorted Array II (有圖)
    • # 88 Merge Sorted Array (有圖)
    • # 125 Valid Palindrome
    • #167 Two Sum II - Input array is sorted (有圖)
    • # 283 Move Zeroes (有圖)
    • # 38 Count and Say
    • # 557. Reverse Words in a String III
    • #977 Squares of a Sorted Array
    • #209 Minimum Size Subarray Sum
  • String
    • # 13 Roman to Integer (有圖)
    • # 771 Jewels and Stones
    • # 937 Reorder Data in Log Files
    • # 929 Unique Email Addresses
    • # 1108 Defanging an IP Address
    • #14 Longest Common Prefix
    • # 387 First Unique Character in a String (有圖)
    • #193 Valid Phone Numbers
    • # 28 Implement strStr()
    • #383 Ransom Note
  • Stack
    • # 20 Valid Parentheses (有圖)
    • # 155 Min Stack
    • BF 165. remove characters
    • #1047 Remove All Adjacent Duplicates In String
  • Binary Search
    • # 1064 Fixed Point (有圖)
    • # 852 Peak Index in a Mountain Array
  • Recursion 遞迴
    • #2625. Flatten Deeply Nested Array
  • Math
    • # 7 Reverse Integer
    • # 9 Palindrome Number (有圖)
    • #53 Maximum Subarray (有圖)
    • # 1085 Sum of Digits in the Minimum Number.
    • # 136 Single Number
    • # 204 Count Primes (有圖)
    • #243 Shortest Word Distance
  • Dynamic Programing
    • # 322 Coin Change
    • # 509 Fibonacci Number (有圖)
    • # 70 Climbing Stairs
    • # 198 House Robber
    • # 168. Excel Sheet Column Title
  • Others
    • # 205. Isomorphic Strings
    • Implement js Array method
    • Flatten Array/Object
  • Matrix
    • 867. Transpose Matrix
  • Queue
    • DOM tree with queue
  • 排序
    • Different Sort
Powered by GitBook
On this page

Was this helpful?

  1. Dynamic Programing

# 70 Climbing Stairs

DP 題目實在太不熟,要多練習。租學者可以先用暴力解法,再找出其中規則

Previous# 509 Fibonacci Number (有圖)Next# 198 House Robber

Last updated 5 years ago

Was this helpful?

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

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

Note: Given n will be a positive integer.

input: 總共 n 階, 你可以一次走一步或兩步 
output:  幾種方式可以到
Example 1:

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

Input: 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
*/

/**
 * @param {number} n
 * @return {number}
 */
var climbStairs = function(n) {}

怎麼解

一看題目就覺得難果然是 DP , DP 對我來說真的是太不熟練了。這題其實是變相費式數列

  • n = 1, result 1 (爬一階 1 次)

  • n = 2, result 1 + 1 (爬一階 2 次 / 爬兩階 1 次)

  • n = 3, result 1 + 2 (前面兩個相加) (爬一階 3 次 / 爬兩階 1 次 + 爬一階 1 次 / 爬一階 1 次 + 爬兩階 1 次 )

  • n = 4, result = 3 + 2 (前面兩個相加)

if(n == 1){
    return 1
}else if(n == 2){
    return 2
}
lookup[i] = lookup[i-1] + lookup[i-2]; 

是不是很像 XD

var climbStairs = function(n) {
    if(n == 1){
        return 1
    }else if(n == 2){
        return 2
    }
    let lookup = [1,2]; // 1 step 有一種方式, 2 step 有兩種方式
    for(let i = 2; i< n ; i++){
        lookup[i] = lookup[i - 1] + lookup[i - 2]
    }
    return lookup[n - 1]
};
console.log(climbStairs(3))
LeetCode