Sort / as the first character in ArrayMap and ArraySet (#50 closes #4)

Author: nedtwigg

Diff for: python/selfie-lib/selfie_lib/ArrayMap.py

@@ -1,35 +1,69 @@
 from collections.abc import Set, Iterator, Mapping
-from typing import List, TypeVar, Union
+from typing import List, TypeVar, Union, Any
 from abc import abstractmethod, ABC
 
 T = TypeVar("T")
 V = TypeVar("V")
 K = TypeVar("K")
 
 
+def _compare_normal(a, b) -> int:
+    if a == b:
+        return 0
+    elif a < b:
+        return -1
+    else:
+        return 1
+
+
+def _compare_string_slash_first(a: str, b: str) -> int:
+    return _compare_normal(a.replace("/", "\0"), b.replace("/", "\0"))
+
+
+def _binary_search(data, item) -> int:
+    compare_func = (
+        _compare_string_slash_first if isinstance(item, str) else _compare_normal
+    )
+    low, high = 0, len(data) - 1
+    while low <= high:
+        mid = (low + high) // 2
+        mid_val = data[mid]
+        comparison = compare_func(mid_val, item)
+
+        if comparison < 0:
+            low = mid + 1
+        elif comparison > 0:
+            high = mid - 1
+        else:
+            return mid  # item found
+    return -(low + 1)  # item not found
+
+
 class ListBackedSet(Set[T], ABC):
     @abstractmethod
     def __len__(self) -> int: ...
 
     @abstractmethod
     def __getitem__(self, index: Union[int, slice]) -> Union[T, List[T]]: ...
 
-    def __contains__(self, item: object) -> bool:
-        for i in range(len(self)):
-            if self[i] == item:
-                return True
-        return False
+    @abstractmethod
+    def __iter__(self) -> Iterator[T]: ...
+
+    def __contains__(self, item: Any) -> bool:
+        return self._binary_search(item) >= 0
+
+    def _binary_search(self, item: Any) -> int:
+        return _binary_search(self, item)
 
 
 class ArraySet(ListBackedSet[K]):
     __data: List[K]
 
-    def __init__(self, data: List[K]):
-        raise NotImplementedError("Use ArraySet.empty() instead")
+    def __init__(self):
+        raise NotImplementedError("Use ArraySet.empty() or other class methods instead")
 
     @classmethod
     def __create(cls, data: List[K]) -> "ArraySet[K]":
-        # Create a new instance without calling __init__
         instance = super().__new__(cls)
         instance.__data = data
         return instance
@@ -40,82 +74,74 @@ def __iter__(self) -> Iterator[K]:
     @classmethod
     def empty(cls) -> "ArraySet[K]":
         if not hasattr(cls, "__EMPTY"):
-            cls.__EMPTY = cls([])
+            cls.__EMPTY = cls.__create([])
         return cls.__EMPTY
 
     def __len__(self) -> int:
         return len(self.__data)
 
     def __getitem__(self, index: Union[int, slice]) -> Union[K, List[K]]:
-        if isinstance(index, int):
-            return self.__data[index]
-        elif isinstance(index, slice):
-            return self.__data[index]
-        else:
-            raise TypeError("Invalid argument type.")
+        return self.__data[index]
 
     def plusOrThis(self, element: K) -> "ArraySet[K]":
-        # TODO: use binary search, and also special sort order for strings
-        if element in self.__data:
+        index = self._binary_search(element)
+        if index >= 0:
             return self
         else:
+            insert_at = -(index + 1)
             new_data = self.__data[:]
-            new_data.append(element)
-            new_data.sort()  # type: ignore[reportOperatorIssue]
+            new_data.insert(insert_at, element)
             return ArraySet.__create(new_data)
 
 
 class ArrayMap(Mapping[K, V]):
-    def __init__(self, data: list):
-        # TODO: hide this constructor as done in ArraySet
-        self.__data = data
+    __data: List[Union[K, V]]
+
+    def __init__(self):
+        raise NotImplementedError("Use ArrayMap.empty() or other class methods instead")
+
+    @classmethod
+    def __create(cls, data: List[Union[K, V]]) -> "ArrayMap[K, V]":
+        instance = cls.__new__(cls)
+        instance.__data = data
+        return instance
 
     @classmethod
     def empty(cls) -> "ArrayMap[K, V]":
         if not hasattr(cls, "__EMPTY"):
-            cls.__EMPTY = cls([])
+            cls.__EMPTY = cls.__create([])
         return cls.__EMPTY
 
     def __getitem__(self, key: K) -> V:
-        index = self.__binary_search_key(key)
+        index = self._binary_search_key(key)
         if index >= 0:
-            return self.__data[2 * index + 1]
+            return self.__data[2 * index + 1]  # type: ignore
         raise KeyError(key)
 
     def __iter__(self) -> Iterator[K]:
-        return (self.__data[i] for i in range(0, len(self.__data), 2))
+        return (self.__data[i] for i in range(0, len(self.__data), 2))  # type: ignore
 
     def __len__(self) -> int:
         return len(self.__data) // 2
 
-    def __binary_search_key(self, key: K) -> int:
-        # TODO: special sort order for strings
-        low, high = 0, (len(self.__data) // 2) - 1
-        while low <= high:
-            mid = (low + high) // 2
-            mid_key = self.__data[2 * mid]
-            if mid_key < key:
-                low = mid + 1
-            elif mid_key > key:
-                high = mid - 1
-            else:
-                return mid
-        return -(low + 1)
+    def _binary_search_key(self, key: K) -> int:
+        keys = [self.__data[i] for i in range(0, len(self.__data), 2)]
+        return _binary_search(keys, key)
 
     def plus(self, key: K, value: V) -> "ArrayMap[K, V]":
-        index = self.__binary_search_key(key)
+        index = self._binary_search_key(key)
         if index >= 0:
             raise ValueError("Key already exists")
         insert_at = -(index + 1)
         new_data = self.__data[:]
-        new_data[insert_at * 2 : insert_at * 2] = [key, value]
-        return ArrayMap(new_data)
+        new_data.insert(insert_at * 2, key)
+        new_data.insert(insert_at * 2 + 1, value)
+        return ArrayMap.__create(new_data)
 
-    def minus_sorted_indices(self, indicesToRemove: List[int]) -> "ArrayMap[K, V]":
-        if not indicesToRemove:
-            return self
-        newData = []
-        for i in range(0, len(self.__data), 2):
-            if i // 2 not in indicesToRemove:
-                newData.extend(self.__data[i : i + 2])
-        return ArrayMap(newData)
+    def minus_sorted_indices(self, indices: List[int]) -> "ArrayMap[K, V]":
+        new_data = self.__data[:]
+        adjusted_indices = [i * 2 for i in indices] + [i * 2 + 1 for i in indices]
+        adjusted_indices.sort(reverse=True)
+        for index in adjusted_indices:
+            del new_data[index]
+        return ArrayMap.__create(new_data)