You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
38 lines
876 B
38 lines
876 B
6 months ago
|
=begin
|
||
|
|
File: climbing_stairs_backtrack.rb
|
||
|
|
Created Time: 2024-05-29
|
||
|
|
Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
|
||
|
|
=end
|
||
|
|
|
||
|
|
### 回溯 ###
|
||
|
|
def backtrack(choices, state, n, res)
|
||
|
|
# 當爬到第 n 階時，方案數量加 1
|
||
|
|
res[0] += 1 if state == n
|
||
|
|
# 走訪所有選擇
|
||
|
|
for choice in choices
|
||
|
|
# 剪枝：不允許越過第 n 階
|
||
|
|
next if state + choice > n
|
||
|
|
|
||
|
|
# 嘗試：做出選擇，更新狀態
|
||
|
|
backtrack(choices, state + choice, n, res)
|
||
|
|
end
|
||
|
|
# 回退
|
||
|
|
end
|
||
|
|
|
||
|
|
### 爬樓梯：回溯 ###
|
||
|
|
def climbing_stairs_backtrack(n)
|
||
|
|
choices = [1, 2] # 可選擇向上爬 1 階或 2 階
|
||
|
|
state = 0 # 從第 0 階開始爬
|
||
|
|
res = [0] # 使用 res[0] 記錄方案數量
|
||
|
|
backtrack(choices, state, n, res)
|
||
|
|
res.first
|
||
|
|
end
|
||
|
|
|
||
|
|
### Driver Code ###
|
||
|
|
if __FILE__ == $0
|
||
|
|
n = 9
|
||
|
|
|
||
|
|
res = climbing_stairs_backtrack(n)
|
||
|
|
puts "爬 #{n} 階樓梯共有 #{res} 種方案"
|
||
|
|
end
|