build

docs/chapter_backtracking/backtracking_algorithm.md

@@ -217,6 +217,12 @@ comments: true
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="preorder_traversal_i_compact.rb"
+    [class]{}-[func]{pre_order}
+    ```
+
 === "Zig"
 
     ```zig title="preorder_traversal_i_compact.zig"
@@ -513,6 +519,12 @@ comments: true
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="preorder_traversal_ii_compact.rb"
+    [class]{}-[func]{pre_order}
+    ```
+
 === "Zig"
 
     ```zig title="preorder_traversal_ii_compact.zig"
@@ -851,6 +863,12 @@ comments: true
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="preorder_traversal_iii_compact.rb"
+    [class]{}-[func]{pre_order}
+    ```
+
 === "Zig"
 
     ```zig title="preorder_traversal_iii_compact.zig"
@@ -1159,6 +1177,32 @@ comments: true
 === "Kotlin"
 
     ```kotlin title=""
+    /* 回溯算法框架 */
+    fun backtrack(state: State?, choices: List<Choice?>, res: List<State?>?) {
+        // 判断是否为解
+        if (isSolution(state)) {
+            // 记录解
+            recordSolution(state, res)
+            // 不再继续搜索
+            return
+        }
+        // 遍历所有选择
+        for (choice in choices) {
+            // 剪枝：判断选择是否合法
+            if (isValid(state, choice)) {
+                // 尝试：做出选择，更新状态
+                makeChoice(state, choice)
+                backtrack(state, choices, res)
+                // 回退：撤销选择，恢复到之前的状态
+                undoChoice(state, choice)
+            }
+        }
+    }
+    ```
+
+=== "Ruby"
+
+    ```ruby title=""
 
     ```
 
@@ -1796,6 +1840,22 @@ comments: true
     }
     ```
 
+=== "Ruby"
+
+    ```ruby title="preorder_traversal_iii_template.rb"
+    [class]{}-[func]{is_solution}
+
+    [class]{}-[func]{record_solution}
+
+    [class]{}-[func]{is_valid}
+
+    [class]{}-[func]{make_choice}
+
+    [class]{}-[func]{undo_choice}
+
+    [class]{}-[func]{backtrack}
+    ```
+
 === "Zig"
 
     ```zig title="preorder_traversal_iii_template.zig"