feat: Add Ruby code - chapter "Backtracking" (#1373)

* [feat] add ruby code - chapter backtracking

* feat: add ruby code block - chapter backtracking

codes/ruby/chapter_backtracking/subset_sum_i_naive.rb

@@ -0,0 +1,46 @@
+=begin
+File: subset_sum_i_naive.rb
+Created Time: 2024-05-22
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+### 回溯算法：子集和 I ###
+def backtrack(state, target, total, choices, res)
+  # 子集和等于 target 时，记录解
+  if total == target
+    res << state.dup
+    return
+  end
+
+  # 遍历所有选择
+  for i in 0...choices.length
+    # 剪枝：若子集和超过 target ，则跳过该选择
+    next if total + choices[i] > target
+    # 尝试：做出选择，更新元素和 total
+    state << choices[i]
+    # 进行下一轮选择
+    backtrack(state, target, total + choices[i], choices, res)
+    # 回退：撤销选择，恢复到之前的状态
+    state.pop
+  end
+end
+
+### 求解子集和 I（包含重复子集）###
+def subset_sum_i_naive(nums, target)
+  state = [] # 状态（子集）
+  total = 0 # 子集和
+  res = [] # 结果列表（子集列表）
+  backtrack(state, target, total, nums, res)
+  res
+end
+
+### Driver Code ###
+if __FILE__ == $0
+  nums = [3, 4, 5]
+  target = 9
+  res = subset_sum_i_naive(nums, target)
+
+  puts "输入数组 nums = #{nums}, target = #{target}"
+  puts "所有和等于 #{target} 的子集 res = #{res}"
+  puts "请注意，该方法输出的结果包含重复集合"
+end