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C++ backend for Binary Indexed Trees (#561)
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‎pydatastructs/trees/_backend/cpp/BinaryIndexedTree.hpp‎

Lines changed: 162 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,162 @@
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#ifndef TREES_BINARYINDEXEDTREE_HPP
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#define TREES_BINARYINDEXEDTREE_HPP
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#define PY_SSIZE_T_CLEAN
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#include <Python.h>
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#include <structmember.h>
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#include <cstdlib>
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#include "../../../utils/_backend/cpp/utils.hpp"
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#include "../../../utils/_backend/cpp/TreeNode.hpp"
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#include "../../../linear_data_structures/_backend/cpp/arrays/ArrayForTrees.hpp"
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#include "../../../linear_data_structures/_backend/cpp/arrays/DynamicOneDimensionalArray.hpp"
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// Copied binary trees and changed the name to BinaryIndexedTree
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// Start from the struct
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typedef struct {
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PyObject_HEAD
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OneDimensionalArray* array;
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PyObject* tree;
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PyObject* flag;
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} BinaryIndexedTree;
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static void BinaryIndexedTree_dealloc(BinaryIndexedTree *self) {
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Py_TYPE(self)->tp_free(reinterpret_cast<PyObject*>(self));
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}
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static PyObject* BinaryIndexedTree_update(BinaryIndexedTree* self, PyObject *args) {
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long index = PyLong_AsLong(PyObject_GetItem(args, PyZero));
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long value = PyLong_AsLong(PyObject_GetItem(args, PyOne));
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long _index = index;
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long _value = value;
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if (PyList_GetItem(self->flag, index) == PyZero) {
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PyList_SetItem(self->flag, index, PyOne);
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index += 1;
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while (index < self->array->_size + 1) {
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long curr = PyLong_AsLong(PyList_GetItem(self->tree, index));
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PyList_SetItem(self->tree, index, PyLong_FromLong(curr + value));
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index = index + (index & (-1*index));
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}
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}
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else {
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value = value - PyLong_AsLong(self->array->_data[index]);
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index += 1;
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while (index < self->array->_size + 1) {
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long curr = PyLong_AsLong(PyList_GetItem(self->tree, index));
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PyList_SetItem(self->tree, index, PyLong_FromLong(curr + value));
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index = index + (index & (-1*index));
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}
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}
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self->array->_data[_index] = PyLong_FromLong(_value);
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Py_RETURN_NONE;
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}
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static PyObject* BinaryIndexedTree___new__(PyTypeObject* type, PyObject *args, PyObject *kwds) {
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BinaryIndexedTree *self;
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self = reinterpret_cast<BinaryIndexedTree*>(type->tp_alloc(type, 0));
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// Python code is such that arguments are: type(array[0]) and array
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if (PyType_Ready(&OneDimensionalArrayType) < 0) { // This has to be present to finalize a type object. This should be called on all type objects to finish their initialization.
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return NULL;
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}
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PyObject* _one_dimensional_array = OneDimensionalArray___new__(&OneDimensionalArrayType, args, kwds);
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if ( !_one_dimensional_array ) {
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return NULL;
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}
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self->array = reinterpret_cast<OneDimensionalArray*>(_one_dimensional_array);
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self->tree = PyList_New(self->array->_size+2);
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for(int i=0;i<self->array->_size+2;i++){
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PyList_SetItem(self->tree, i, PyZero);
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}
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self->flag = PyList_New(self->array->_size);
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for(int i=0;i<self->array->_size;i++){
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PyList_SetItem(self->flag, i, PyZero);
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BinaryIndexedTree_update(self, Py_BuildValue("(OO)", PyLong_FromLong(i), self->array->_data[i]));
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}
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return reinterpret_cast<PyObject*>(self);
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}
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static PyObject* BinaryIndexedTree_get_prefix_sum(BinaryIndexedTree* self, PyObject *args) {
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long index = PyLong_AsLong(PyObject_GetItem(args, PyZero));
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index += 1;
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long sum = 0;
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while (index > 0) {
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sum += PyLong_AsLong(PyList_GetItem(self->tree, index));
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index = index - (index & (-1*index));
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}
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return PyLong_FromLong(sum);
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}
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static PyObject* BinaryIndexedTree_get_sum(BinaryIndexedTree* self, PyObject *args) {
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long left_index = PyLong_AsLong(PyObject_GetItem(args, PyZero));
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long right_index = PyLong_AsLong(PyObject_GetItem(args, PyOne));
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if (left_index >= 1) {
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long l1 = PyLong_AsLong(BinaryIndexedTree_get_prefix_sum(self, Py_BuildValue("(O)", PyLong_FromLong(right_index))));
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long l2 = PyLong_AsLong(BinaryIndexedTree_get_prefix_sum(self, Py_BuildValue("(O)", PyLong_FromLong(left_index - 1))));
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return PyLong_FromLong(l1 - l2);
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}
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else {
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return BinaryIndexedTree_get_prefix_sum(self, Py_BuildValue("(O)", PyLong_FromLong(right_index)));
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}
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}
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static struct PyMethodDef BinaryIndexedTree_PyMethodDef[] = {
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{"update", (PyCFunction) BinaryIndexedTree_update, METH_VARARGS, NULL},
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{"get_prefix_sum", (PyCFunction) BinaryIndexedTree_get_prefix_sum, METH_VARARGS, NULL},
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{"get_sum", (PyCFunction) BinaryIndexedTree_get_sum, METH_VARARGS, NULL},
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{NULL}
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};
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static PyMemberDef BinaryIndexedTree_PyMemberDef[] = {
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{"array", T_OBJECT_EX, offsetof(BinaryIndexedTree, array), 0, "array"},
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{"tree", T_OBJECT_EX, offsetof(BinaryIndexedTree, tree), 0, "tree"},
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{"flag", T_OBJECT_EX, offsetof(BinaryIndexedTree, flag), 0, "flag"},
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{NULL} /* Sentinel */
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};
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static PyTypeObject BinaryIndexedTreeType = {
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/* tp_name */ PyVarObject_HEAD_INIT(NULL, 0) "BinaryIndexedTree",
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/* tp_basicsize */ sizeof(BinaryIndexedTree),
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/* tp_itemsize */ 0,
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/* tp_dealloc */ (destructor) BinaryIndexedTree_dealloc,
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/* tp_print */ 0,
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/* tp_getattr */ 0,
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/* tp_setattr */ 0,
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/* tp_reserved */ 0,
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/* tp_repr */ 0,
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/* tp_as_number */ 0,
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/* tp_as_sequence */ 0,
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/* tp_as_mapping */ 0,
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/* tp_hash */ 0,
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/* tp_call */ 0,
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/* tp_str */ 0,
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/* tp_getattro */ 0,
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/* tp_setattro */ 0,
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/* tp_as_buffer */ 0,
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/* tp_flags */ Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
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/* tp_doc */ 0,
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/* tp_traverse */ 0,
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/* tp_clear */ 0,
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/* tp_richcompare */ 0,
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/* tp_weaklistoffset */ 0,
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/* tp_iter */ 0,
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/* tp_iternext */ 0,
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/* tp_methods */ BinaryIndexedTree_PyMethodDef,
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/* tp_members */ BinaryIndexedTree_PyMemberDef,
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/* tp_getset */ 0,
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/* tp_base */ &PyBaseObject_Type,
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/* tp_dict */ 0,
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/* tp_descr_get */ 0,
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/* tp_descr_set */ 0,
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/* tp_dictoffset */ 0,
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/* tp_init */ 0,
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/* tp_alloc */ 0,
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/* tp_new */ BinaryIndexedTree___new__,
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};
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#endif

‎pydatastructs/trees/_backend/cpp/trees.cpp‎

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -4,6 +4,7 @@
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#include "BinaryTreeTraversal.hpp"
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#include "SelfBalancingBinaryTree.hpp"
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#include "RedBlackTree.hpp"
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#include "BinaryIndexedTree.hpp"
78

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static struct PyModuleDef trees_struct = {
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PyModuleDef_HEAD_INIT,
@@ -47,5 +48,11 @@ PyMODINIT_FUNC PyInit__trees(void) {
4748
Py_INCREF(&RedBlackTreeType);
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PyModule_AddObject(trees, "RedBlackTree", reinterpret_cast<PyObject*>(&RedBlackTreeType));
4950

51+
if (PyType_Ready(&BinaryIndexedTreeType) < 0) {
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return NULL;
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}
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Py_INCREF(&BinaryIndexedTreeType);
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PyModule_AddObject(trees, "BinaryIndexedTree", reinterpret_cast<PyObject*>(&BinaryIndexedTreeType));
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return trees;
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}

‎pydatastructs/trees/binary_trees.py‎

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1760,8 +1760,9 @@ class BinaryIndexedTree(object):
17601760
__slots__ = ['tree', 'array', 'flag']
17611761

17621762
def __new__(cls, array, **kwargs):
1763-
raise_if_backend_is_not_python(
1764-
cls, kwargs.get('backend', Backend.PYTHON))
1763+
backend = kwargs.get('backend', Backend.PYTHON)
1764+
if backend == Backend.CPP:
1765+
return _trees.BinaryIndexedTree(type(array[0]), array, **kwargs)
17651766
obj = object.__new__(cls)
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obj.array = OneDimensionalArray(type(array[0]), array)
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obj.tree = [0] * (obj.array._size + 2)

‎pydatastructs/trees/tests/test_binary_trees.py‎

Lines changed: 7 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -361,11 +361,11 @@ def test_select_rank(expected_output):
361361
test_select_rank([])
362362

363363

364-
def test_BinaryIndexedTree():
364+
def _test_BinaryIndexedTree(backend):
365365

366366
FT = BinaryIndexedTree
367367

368-
t = FT([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
368+
t = FT([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], backend=backend)
369369

370370
assert t.get_sum(0, 2) == 6
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assert t.get_sum(0, 4) == 15
@@ -375,6 +375,11 @@ def test_BinaryIndexedTree():
375375
assert t.get_sum(0, 4) == 114
376376
assert t.get_sum(1, 9) == 54
377377

378+
def test_BinaryIndexedTree():
379+
_test_BinaryIndexedTree(Backend.PYTHON)
380+
381+
def test_cpp_BinaryIndexedTree():
382+
_test_BinaryIndexedTree(Backend.CPP)
378383

379384
def test_CartesianTree():
380385
tree = CartesianTree()

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