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.

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

ja/codes/python/chapter_backtracking/permutations_ii.py

@@ -0,0 +1,46 @@
+"""
+File: permutations_ii.py
+Created Time: 2023-04-15
+Author: krahets (krahets@163.com)
+"""
+
+
+def backtrack(
+    state: list[int], choices: list[int], selected: list[bool], res: list[list[int]]
+):
+    """バックトラッキングアルゴリズム：順列 II"""
+    # 状態の長さが要素数と等しいとき、解を記録
+    if len(state) == len(choices):
+        res.append(list(state))
+        return
+    # すべての選択肢を走査
+    duplicated = set[int]()
+    for i, choice in enumerate(choices):
+        # 枝刈り：要素の重複選択を許可せず、等しい要素の重複選択も許可しない
+        if not selected[i] and choice not in duplicated:
+            # 試行：選択を行い、状態を更新
+            duplicated.add(choice)  # 選択された要素値を記録
+            selected[i] = True
+            state.append(choice)
+            # 次の選択ラウンドに進む
+            backtrack(state, choices, selected, res)
+            # 撤回：選択を取り消し、前の状態に復元
+            selected[i] = False
+            state.pop()
+
+
+def permutations_ii(nums: list[int]) -> list[list[int]]:
+    """順列 II"""
+    res = []
+    backtrack(state=[], choices=nums, selected=[False] * len(nums), res=res)
+    return res
+
+
+"""ドライバーコード"""
+if __name__ == "__main__":
+    nums = [1, 2, 2]
+
+    res = permutations_ii(nums)
+
+    print(f"入力配列 nums = {nums}")
+    print(f"すべての順列 res = {res}")