feat: add isRed and setChild

src/rbt.c

@@ -0,0 +1,157 @@
+#include "rbt.h"
+
+static bool isRed(const RbtNode* n)
+{
+    return n != nullptr && n->red;
+}
+
+static void setChild(RbTree* t, RbtNode* parent, RbtNode* oldChild, RbtNode* newChild)
+{
+    if (parent == nullptr)
+        t->root = newChild;
+    else if (parent->left == oldChild)
+        parent->left = newChild;
+    else
+        parent->right = newChild;
+}
+
+static void rotateLeft(RbTree* t, RbtNode* x)
+{
+    RbtNode* y = x->right;
+    x->right = y->left;
+    if (y->left != nullptr)
+        y->left->parent = x;
+    y->parent = x->parent;
+    setChild(t, x->parent, x, y);
+    y->left = x;
+    x->parent = y;
+}
+
+static void rotateRight(RbTree* t, RbtNode* x)
+{
+    RbtNode* y = x->left;
+    x->left = y->right;
+    if (y->right != nullptr)
+        y->right->parent = x;
+    y->parent = x->parent;
+    setChild(t, x->parent, x, y);
+    y->right = x;
+    x->parent = y;
+}
+
+static void insertFixup(RbTree* t, RbtNode* z)
+{
+    while (isRed(z->parent)) {
+        RbtNode* parent = z->parent;
+        RbtNode* grandparent = parent->parent;
+
+        if (parent == grandparent->left) {
+            RbtNode* uncle = grandparent->right;
+            if (isRed(uncle)) {
+                parent->red = false;
+                uncle->red = false;
+                grandparent->red = true;
+                z = grandparent;
+            } else {
+                if (z == parent->right) {
+                    z = parent;
+                    rotateLeft(t, z);
+                    parent = z->parent;
+                }
+                parent->red = false;
+                grandparent->red = true;
+                rotateRight(t, grandparent);
+            }
+        } else {
+            RbtNode* uncle = grandparent->left;
+            if (isRed(uncle)) {
+                parent->red = false;
+                uncle->red = false;
+                grandparent->red = true;
+                z = grandparent;
+            } else {
+                if (z == parent->left) {
+                    z = parent;
+                    rotateRight(t, z);
+                    parent = z->parent;
+                }
+                parent->red = false;
+                grandparent->red = true;
+                rotateLeft(t, grandparent);
+            }
+        }
+    }
+    t->root->red = false;
+}
+
+static void removeFixup(RbTree* t, RbtNode* x, RbtNode* xParent)
+{
+    while (x != t->root && !isRed(x)) {
+        if (x == xParent->left) {
+            RbtNode* w = xParent->right;
+            if (isRed(w)) {
+                w->red = false;
+                xParent->red = true;
+                rotateLeft(t, xParent);
+                w = xParent->right;
+            }
+            if (!isRed(w->left) && !isRed(w->right)) {
+                w->red = true;
+                x = xParent;
+                xParent = x->parent;
+            } else {
+                if (!isRed(w->right)) {
+                    if (w->left != nullptr)
+                        w->left->red = false;
+                    w->red = true;
+                    rotateRight(t, w);
+                    w = xParent->right;
+                }
+                w->red = xParent->red;
+                xParent->red = false;
+                if (w->right != nullptr)
+                    w->right->red = false;
+                rotateLeft(t, xParent);
+                x = t->root;
+                xParent = nullptr;
+            }
+        } else {
+            RbtNode* w = xParent->left;
+            if (isRed(w)) {
+                w->red = false;
+                xParent->red = true;
+                rotateRight(t, xParent);
+                w = xParent->left;
+            }
+            if (!isRed(w->left) && !isRed(w->right)) {
+                w->red = true;
+                x = xParent;
+                xParent = x->parent;
+            } else {
+                if (!isRed(w->left)) {
+                    if (w->right != nullptr)
+                        w->right->red = false;
+                    w->red = true;
+                    rotateLeft(t, w);
+                    w = xParent->left;
+                }
+                w->red = xParent->red;
+                xParent->red = false;
+                if (w->left != nullptr)
+                    w->left->red = false;
+                rotateRight(t, xParent);
+                x = t->root;
+                xParent = nullptr;
+            }
+        }
+    }
+    if (x != nullptr)
+        x->red = false;
+}
+
+void rbtInit(RbTree* t)
+{
+    t->root = nullptr;
+    t->count = 0;
+}
+