Bug fixes and improvements (#1380)

* preorder, inorder, postorder -> pre-order, in-order, post-order

* Bug fixes

* Bug fixes

* Update what_is_dsa.md

* Sync zh and zh-hant versions

* Sync zh and zh-hant versions.

* Update performance_evaluation.md and time_complexity.md

* Add @khoaxuantu to the landing page.

* Sync zh and zh-hant versions

* Add @ khoaxuantu to the landing page of zh-hant and en versions.

zh-hant/codes/ruby/chapter_greedy/fractional_knapsack.rb

@@ -0,0 +1,51 @@
+=begin
+File: fractional_knapsack.rb
+Created Time: 2024-05-07
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+### 物品 ###
+class Item
+  attr_accessor :w # 物品重量
+  attr_accessor :v # 物品價值
+
+  def initialize(w, v)
+    @w = w
+    @v = v
+  end
+end
+
+### 分數背包：貪婪 ###
+def fractional_knapsack(wgt, val, cap)
+  # 建立物品串列，包含兩個屬性：重量，價值
+  items = wgt.each_with_index.map { |w, i| Item.new(w, val[i]) }
+  # 按照單位價值 item.v / item.w 從高到低進行排序
+  items.sort! { |a, b| (b.v.to_f / b.w) <=> (a.v.to_f / a.w) }
+  # 迴圈貪婪選擇
+  res = 0
+  for item in items
+    if item.w <= cap
+      # 若剩餘容量充足，則將當前物品整個裝進背包
+      res += item.v
+      cap -= item.w
+    else
+      # 若剩餘容量不足，則將當前物品的一部分裝進背包
+      res += (item.v.to_f / item.w) * cap
+      # 已無剩餘容量，因此跳出迴圈
+      break
+    end
+  end
+  res
+end
+
+### Driver Code ###
+if __FILE__ == $0
+  wgt = [10, 20, 30, 40, 50]
+  val = [50, 120, 150, 210, 240]
+  cap = 50
+  n = wgt.length
+
+  # 貪婪演算法
+  res = fractional_knapsack(wgt, val, cap)
+  puts "不超過背包容量的最大物品價值為 #{res}"
+end