build

chapter_divide_and_conquer/build_binary_tree_problem.md

@@ -171,9 +171,35 @@ status: new
 === "Go"
 
     ```go title="build_tree.go"
-    [class]{}-[func]{dfs}
+    /* 构建二叉树：分治 */
+    func dfsBuildTree(preorder, inorder []int, hmap map[int]int, i, l, r int) *TreeNode {
+        // 子树区间为空时终止
+        if r-l < 0 {
+            return nil
+        }
+        // 初始化根节点
+        root := NewTreeNode(preorder[i])
+        // 查询 m ，从而划分左右子树
+        m := hmap[preorder[i]]
+        // 子问题：构建左子树
+        root.Left = dfsBuildTree(preorder, inorder, hmap, i+1, l, m-1)
+        // 子问题：构建右子树
+        root.Right = dfsBuildTree(preorder, inorder, hmap, i+1+m-l, m+1, r)
+        // 返回根节点
+        return root
+    }
 
-    [class]{}-[func]{buildTree}
+    /* 构建二叉树 */
+    func buildTree(preorder, inorder []int) *TreeNode {
+        // 初始化哈希表，存储 inorder 元素到索引的映射
+        hmap := make(map[int]int, len(inorder))
+        for i := 0; i < len(inorder); i++ {
+            hmap[inorder[i]] = i
+        }
+
+        root := dfsBuildTree(preorder, inorder, hmap, 0, 0, len(inorder)-1)
+        return root
+    }
     ```
 
 === "JavaScript"