_left_right_rotate() for SBBT

Author: Kishan-Ved

pydatastructs/trees/_backend/cpp/SelfBalancingBinaryTree.hpp

@@ -137,6 +137,47 @@ static PyObject* SelfBalancingBinaryTree__left_rotate(SelfBalancingBinaryTree* s
     Py_RETURN_NONE;
 }
 
+static PyObject* SelfBalancingBinaryTree__left_right_rotate(SelfBalancingBinaryTree* self, PyObject *args) {
+    PyObject* j = PyObject_GetItem(args, PyZero);
+    PyObject* k = PyObject_GetItem(args, PyOne);
+    BinaryTree* bt = self->bst->binary_tree;
+
+    PyObject* i = reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(k)])->right;
+    PyObject* v = reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(i)])->left;
+    PyObject* w = reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(i)])->right;
+
+    reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(k)])->right = v;
+    reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(j)])->left = w;
+
+    if (v != Py_None) {
+        reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(v)])->parent = k;
+    }
+    if (w != Py_None) {
+        reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(w)])->parent = j;
+    }
+
+    reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(i)])->left = k;
+    reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(i)])->right = j;
+    reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(i)])->parent = reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(j)])->parent;
+
+    reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(k)])->parent = i;
+    reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(j)])->parent = i;
+
+    PyObject* ip = reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(i)])->parent;
+    if (ip != Py_None) {
+        if (reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(ip)])->left == j) {
+            reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(ip)])->left = i;
+        }
+        else {
+            reinterpret_cast<TreeNode*>(bt->tree->_one_dimensional_array->_data[PyLong_AsLong(ip)])->right = i;
+        }
+    }
+    else {
+        bt->root_idx = i;
+    }
+    Py_RETURN_NONE;
+}
+
 static struct PyMethodDef SelfBalancingBinaryTree_PyMethodDef[] = {
     {"insert", (PyCFunction) SelfBalancingBinaryTree_insert, METH_VARARGS | METH_KEYWORDS, NULL},
     {"delete", (PyCFunction) SelfBalancingBinaryTree_delete, METH_VARARGS | METH_KEYWORDS, NULL},
@@ -151,6 +192,7 @@ static struct PyMethodDef SelfBalancingBinaryTree_PyMethodDef[] = {
     {"select", (PyCFunction) SelfBalancingBinaryTree_select, METH_VARARGS, NULL},
     {"_right_rotate", (PyCFunction) SelfBalancingBinaryTree__right_rotate, METH_VARARGS, NULL},
     {"_left_rotate", (PyCFunction) SelfBalancingBinaryTree__left_rotate, METH_VARARGS, NULL},
+    {"_left_right_rotate", (PyCFunction) SelfBalancingBinaryTree__left_right_rotate, METH_VARARGS, NULL},
     {NULL}
 };
 

pydatastructs/trees/tests/test_binary_trees.py

@@ -469,10 +469,13 @@ def _test_SelfBalancingBinaryTree(backend):
     tree.insert(4.56, 4.56)
     tree._left_rotate(5, 8)
     assert tree.tree[tree.tree[8].parent].left == 8
+    assert str(tree) == "[(2, 5, 5, 1), (None, 5.5, 5.5, None), (4, 4.5, 4.5, 3), (8, 4.6, 4.6, 6), (None, 4.4, 4.4, None), (7, 4.55, 4.55, None), (None, 4.65, 4.65, None), (None, 4.54, 4.54, None), (5, 4.56, 4.56, None)]"
+
+    tree._left_right_rotate(0, 2)
+    assert str(tree) == "[(6, 5, 5, 1), (None, 5.5, 5.5, None), (4, 4.5, 4.5, 8), (2, 4.6, 4.6, 0), (None, 4.4, 4.4, None), (7, 4.55, 4.55, None), (None, 4.65, 4.65, None), (None, 4.54, 4.54, None), (5, 4.56, 4.56, None)]"
 
 def test_SelfBalancingBinaryTree():
     _test_SelfBalancingBinaryTree(Backend.PYTHON)
-
 def test_cpp_SelfBalancingBinaryTree():
     _test_SelfBalancingBinaryTree(Backend.CPP)