build

docs/chapter_backtracking/permutations_problem.md

@@ -506,9 +506,36 @@ comments: true
 === "Ruby"
 
     ```ruby title="permutations_i.rb"
-    [class]{}-[func]{backtrack}
+    ### 回溯算法：全排列 I ###
+    def backtrack(state, choices, selected, res)
+      # 当状态长度等于元素数量时，记录解
+      if state.length == choices.length
+        res << state.dup
+        return
+      end
 
-    [class]{}-[func]{permutations_i}
+      # 遍历所有选择
+      choices.each_with_index do |choice, i|
+        # 剪枝：不允许重复选择元素
+        unless selected[i]
+          # 尝试：做出选择，更新状态
+          selected[i] = true
+          state << choice
+          # 进行下一轮选择
+          backtrack(state, choices, selected, res)
+          # 回退：撤销选择，恢复到之前的状态
+          selected[i] = false
+          state.pop
+        end
+      end
+    end
+
+    ### 全排列 I ###
+    def permutations_i(nums)
+      res = []
+      backtrack([], nums, Array.new(nums.length, false), res)
+      res
+    end
     ```
 
 === "Zig"
@@ -1032,9 +1059,38 @@ comments: true
 === "Ruby"
 
     ```ruby title="permutations_ii.rb"
-    [class]{}-[func]{backtrack}
+    ### 回溯算法：全排列 II ###
+    def backtrack(state, choices, selected, res)
+      # 当状态长度等于元素数量时，记录解
+      if state.length == choices.length
+        res << state.dup
+        return
+      end
 
-    [class]{}-[func]{permutations_ii}
+      # 遍历所有选择
+      duplicated = Set.new
+      choices.each_with_index do |choice, i|
+        # 剪枝：不允许重复选择元素 且 不允许重复选择相等元素
+        if !selected[i] && !duplicated.include?(choice)
+          # 尝试：做出选择，更新状态
+          duplicated.add(choice)
+          selected[i] = true
+          state << choice
+          # 进行下一轮选择
+          backtrack(state, choices, selected, res)
+          # 回退：撤销选择，恢复到之前的状态
+          selected[i] = false
+          state.pop
+        end
+      end
+    end
+
+    ### 全排列 II ###
+    def permutations_ii(nums)
+      res = []
+      backtrack([], nums, Array.new(nums.length, false), res)
+      res
+    end
     ```
 
 === "Zig"