Add CPP version of selection sort (#542)

Author: sak-codes

pydatastructs/linear_data_structures/_backend/cpp/algorithms/algorithms.cpp

@@ -1,12 +1,14 @@
 #include <Python.h>
 #include "quick_sort.hpp"
-#include "bubble_sort.hpp"
+#include "n2_square_sort.hpp"
 
 static PyMethodDef algorithms_PyMethodDef[] = {
     {"quick_sort", (PyCFunction) quick_sort,
      METH_VARARGS | METH_KEYWORDS, ""},
     {"bubble_sort", (PyCFunction) bubble_sort,
      METH_VARARGS | METH_KEYWORDS, ""},
+    {"selection_sort", (PyCFunction) selection_sort,
+     METH_VARARGS | METH_KEYWORDS, ""},
     {NULL, NULL, 0, NULL}        /* Sentinel */
 };
 

pydatastructs/linear_data_structures/_backend/cpp/algorithms/bubble_sort.hpp renamed to pydatastructs/linear_data_structures/_backend/cpp/algorithms/n2_square_sort.hpp

@@ -1,12 +1,13 @@
-#ifndef LINEAR_DATA_STRUCTURES_ALGORITHMS_BUBBLE_SORT_HPP
-#define LINEAR_DATA_STRUCTURES_ALGORITHMS_BUBBLE_SORT_HPP
+#ifndef LINEAR_DATA_STRUCTURES_ALGORITHMS_N2_SQUARE_SORT_HPP
+#define LINEAR_DATA_STRUCTURES_ALGORITHMS_N2_SQUARE_SORT_HPP
 
 #define PY_SSIZE_T_CLEAN
 #include <Python.h>
 #include "../arrays/OneDimensionalArray.hpp"
 #include "../arrays/DynamicOneDimensionalArray.hpp"
 #include "../../../../utils/_backend/cpp/utils.hpp"
 
+// Bubble Sort
 static PyObject* bubble_sort_impl(PyObject* array, size_t lower, size_t upper,
     PyObject* comp, size_t arr_length) {
     for (size_t i = 0; i < arr_length - 1; i++) {
@@ -65,4 +66,65 @@ static PyObject* bubble_sort(PyObject* self, PyObject* args, PyObject* kwds) {
     return args0;
 }
 
+
+// Selection Sort
+static PyObject* selection_sort_impl(PyObject* array, size_t lower, size_t upper,
+    PyObject* comp) {
+    for (size_t i = lower; i < upper + 1; i++) {
+        PyObject* j_min_PyObject = PyLong_FromSize_t(i);
+        PyObject* i_PyObject = PyLong_FromSize_t(i);
+        for (size_t j = i + 1; j < upper + 1; j++) {
+            PyObject* j_PyObject = PyLong_FromSize_t(j);
+            if( _comp(PyObject_GetItem(array, j_min_PyObject),
+                        PyObject_GetItem(array, j_PyObject), comp) != 1 ) {
+                j_min_PyObject = j_PyObject;
+            }
+        }
+        PyObject* tmp = PyObject_GetItem(array, j_min_PyObject);
+        PyObject_SetItem(array, j_min_PyObject,
+                        PyObject_GetItem(array, i_PyObject));
+        PyObject_SetItem(array, i_PyObject, tmp);
+    }
+    return array;
+}
+
+
+static PyObject* selection_sort(PyObject* self, PyObject* args, PyObject* kwds) {
+    PyObject *args0 = NULL, *start = NULL, *end = NULL;
+    PyObject *comp = NULL, *pick_pivot_element = NULL;
+    size_t lower, upper;
+    args0 = PyObject_GetItem(args, PyZero);
+    int is_DynamicOneDimensionalArray = _check_type(args0, &DynamicOneDimensionalArrayType);
+    int is_OneDimensionalArray = _check_type(args0, &OneDimensionalArrayType);
+    if( !is_DynamicOneDimensionalArray && !is_OneDimensionalArray ) {
+        raise_exception_if_not_array(args0);
+        return NULL;
+    }
+    comp = PyObject_GetItem(kwds, PyUnicode_FromString("comp"));
+    if( comp == NULL ) {
+        PyErr_Clear();
+    }
+    start = PyObject_GetItem(kwds, PyUnicode_FromString("start"));
+    if( start == NULL ) {
+        PyErr_Clear();
+        lower = 0;
+    } else {
+        lower = PyLong_AsSize_t(start);
+    }
+    end = PyObject_GetItem(kwds, PyUnicode_FromString("end"));
+    if( end == NULL ) {
+        PyErr_Clear();
+        upper = PyObject_Length(args0) - 1;
+    } else {
+        upper = PyLong_AsSize_t(end);
+    }
+
+    args0 = selection_sort_impl(args0, lower, upper, comp);
+    if( is_DynamicOneDimensionalArray ) {
+        PyObject_CallMethod(args0, "_modify", "O", Py_True);
+    }
+    Py_INCREF(args0);
+    return args0;
+}
+
 #endif

pydatastructs/linear_data_structures/algorithms.py

@@ -1431,8 +1431,9 @@ def selection_sort(array, **kwargs):
 
     .. [1] https://en.wikipedia.org/wiki/Selection_sort
     """
-    raise_if_backend_is_not_python(
-            selection_sort, kwargs.get('backend', Backend.PYTHON))
+    backend = kwargs.pop("backend", Backend.PYTHON)
+    if backend == Backend.CPP:
+        return _algorithms.bubble_sort(array, **kwargs)
     start = kwargs.get('start', 0)
     end = kwargs.get('end', len(array) - 1)
     comp = kwargs.get('comp', lambda u, v: u <= v)

pydatastructs/linear_data_structures/tests/benchmarks/test_algorithms.py

@@ -1,6 +1,6 @@
 import random, timeit, functools, os, pytest
 from pydatastructs import (OneDimensionalArray, Backend,
-    DynamicOneDimensionalArray, quick_sort, bubble_sort)
+    DynamicOneDimensionalArray, quick_sort, bubble_sort, selection_sort)
 
 def _test_common_sort(sort, **kwargs):
     cpp = Backend.CPP
@@ -39,3 +39,8 @@ def test_quick_sort():
 @pytest.mark.xfail
 def test_bubble_sort():
     _test_common_sort(bubble_sort, size=2000)
+
+
+@pytest.mark.xfail
+def test_selection_sort():
+    _test_common_sort(selection_sort, size=2000)

pydatastructs/linear_data_structures/tests/test_algorithms.py

@@ -121,6 +121,7 @@ def test_bubble_sort():
 
 def test_selection_sort():
     _test_common_sort(selection_sort)
+    _test_common_sort(selection_sort, backend=Backend.CPP)
 
 def test_insertion_sort():
     _test_common_sort(insertion_sort)

pydatastructs/utils/testing_util.py

@@ -13,7 +13,7 @@
 
 
 # Root pydatastructs directory
-ROOT_DIR = pathlib.Path(os.path.abspath(__file__)).parents[2]
+ROOT_DIR = pathlib.Path(os.path.abspath(__file__)).parents[1]
 
 
 SKIP_FILES = ['testing_util.py']