docs: add Japanese translate documents (#1812)

* docs: add Japanese documents (`ja/docs`)

* docs: add Japanese documents (`ja/codes`)

* docs: add Japanese documents

* Remove pythontutor blocks in ja/

* Add an empty at the end of each markdown file.

* Add the missing figures (use the English version temporarily).

* Add index.md for Japanese version.

* Add index.html for Japanese version.

* Add missing index.assets

* Fix backtracking_algorithm.md for Japanese version.

* Add avatar_eltociear.jpg. Fix image links on the Japanese landing page.

* Add the Japanese banner.

---------

Co-authored-by: krahets <krahets@163.com>

ja/codes/python/chapter_divide_and_conquer/build_tree.py

@@ -0,0 +1,54 @@
+"""
+File: build_tree.py
+Created Time: 2023-07-15
+Author: krahets (krahets@163.com)
+"""
+
+import sys
+from pathlib import Path
+
+sys.path.append(str(Path(__file__).parent.parent))
+from modules import TreeNode, print_tree
+
+
+def dfs(
+    preorder: list[int],
+    inorder_map: dict[int, int],
+    i: int,
+    l: int,
+    r: int,
+) -> TreeNode | None:
+    """二分木の構築：分割統治"""
+    # 部分木の区間が空のとき終了
+    if r - l < 0:
+        return None
+    # ルートノードを初期化
+    root = TreeNode(preorder[i])
+    # m をクエリして左部分木と右部分木を分割
+    m = inorder_map[preorder[i]]
+    # 部分問題：左部分木を構築
+    root.left = dfs(preorder, inorder_map, i + 1, l, m - 1)
+    # 部分問題：右部分木を構築
+    root.right = dfs(preorder, inorder_map, i + 1 + m - l, m + 1, r)
+    # ルートノードを返す
+    return root
+
+
+def build_tree(preorder: list[int], inorder: list[int]) -> TreeNode | None:
+    """二分木を構築"""
+    # ハッシュテーブルを初期化、中順走査の要素からインデックスへのマッピングを保存
+    inorder_map = {val: i for i, val in enumerate(inorder)}
+    root = dfs(preorder, inorder_map, 0, 0, len(inorder) - 1)
+    return root
+
+
+"""ドライバーコード"""
+if __name__ == "__main__":
+    preorder = [3, 9, 2, 1, 7]
+    inorder = [9, 3, 1, 2, 7]
+    print(f"前順走査 = {preorder}")
+    print(f"中順走査 = {inorder}")
+
+    root = build_tree(preorder, inorder)
+    print("構築された二分木は：")
+    print_tree(root)