From fafc5af2abd04bd8b7c644c3c9be93ae5e019625 Mon Sep 17 00:00:00 2001
From: Georg Hopp <georg@steffers.org>
Date: Fri, 23 Aug 2013 11:24:01 +0100
Subject: [PATCH] cope binarytree to play with an rbtree implementation

---
 src/rbtree.c | 297 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 297 insertions(+)
 create mode 100644 src/rbtree.c

diff --git a/src/rbtree.c b/src/rbtree.c
new file mode 100644
index 0000000..68b7ad2
--- /dev/null
+++ b/src/rbtree.c
@@ -0,0 +1,297 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+
+struct element
+{
+    int data;
+
+    struct element * parent;
+    struct element * left;
+    struct element * right;
+};
+
+struct element *
+newElement(int data)
+{
+    struct element * el = malloc(sizeof(struct element));
+    el->data   = data;
+    el->parent = NULL;
+    el->left   = NULL;
+    el->right  = NULL;
+
+    return el;
+}
+
+/**
+ * find element in tree
+ */
+struct element *
+findElement(struct element * tree, int data)
+{
+    while (NULL != tree) {
+        if (tree->data == data) {
+            break;
+        }
+
+        if (data < tree->data) {
+            tree = tree->left;
+        } else {
+            tree = tree->right;
+        }
+    }
+
+    return tree;
+}
+
+/**
+ * insert element in tree
+ */
+void
+insertElement(struct element ** tree, int data)
+{
+    struct element * node = *tree;
+
+    if (NULL == node) {
+        *tree = newElement(data);
+        return;
+    }
+
+    while (data != node->data) {
+        if (data < node->data) {
+            if (NULL == node->left) {
+                node->left         = newElement(data);
+                node->left->parent = node;
+                return;
+            } else {
+                node = node->left;
+            }
+        } else {
+            if (NULL == node->right) {
+                node->right         = newElement(data);
+                node->right->parent = node;
+                return;
+            } else {
+                node = node->right;
+            }
+        }
+    }
+}
+
+/**
+ * delete element from tree
+ * here multiple functions are involved....
+ * =======================================================================
+ */
+/**
+ * find minimum of the right subtree aka leftmost leaf of right subtree
+ * aka left in-order successor.
+ * We return the parent of the element in the out argument parent.
+ * This can be NULL wenn calling.
+ */
+struct element *
+findInOrderSuccessor(struct element * tree)
+{
+    struct element * node = tree->right;
+
+    while (NULL != node->left) {
+        node = node->left;
+    }
+
+    return node;
+}
+
+void
+deleteElement(struct element ** tree, int data)
+{
+    struct element * node   = *tree;
+
+    // find the relevant node and it's parent
+    while (NULL != node && node->data != data) {
+        if (data < node->data) {
+            node = node->left;
+        } else {
+            node = node->right;
+        }
+    }
+
+    // element not found
+    if (NULL == node) {
+        return;
+    }
+
+    // distinuish 3 cases, where the resolving of each case leads to the
+    // precondition of the other.
+
+    // case 1: two children
+    if (NULL != node->left && NULL != node->right) {
+        struct element * successor = findInOrderSuccessor(node);
+
+        node->data = successor->data;
+        node       = successor;
+    }
+
+    // case 2: one child wither left or right
+    if (NULL != node->left) {
+        //node->data = node->left->data;
+        //node       = node->left;
+        if (NULL != node->parent) {
+            if (node == node->parent->left) {
+                node->parent->left = node->left;
+            } else {
+                node->parent->right = node->left;
+            }
+        }
+        node->left->parent = node->parent;
+    } 
+
+    if (NULL != node->right) {
+        //node->data = node->right->data;
+        //node       = node->right;
+        if (NULL != node->parent) {
+            if (node == node->parent->left) {
+                node->parent->left = node->right;
+            } else {
+                node->parent->right = node->right;
+            }
+        }
+        node->right->parent = node->parent;
+    }
+
+    // case 3: we are a leaf
+    if (NULL != node->parent) {
+        if (node == node->parent->left) {
+            node->parent->left  = NULL;
+        } else {
+            node->parent->right = NULL;
+        }
+    }
+
+    if (node == *tree) {
+        if (NULL != node->left) {
+            *tree = node->left;
+        } else if (NULL != node->right) {
+            *tree = node->right;
+        } else {
+            *tree = NULL;
+        }
+    }
+
+    free(node);
+}
+
+
+void
+traverse(struct element * tree, void (*cb)(int, int))
+{
+    struct element * previous = tree;
+    struct element * node     = tree;
+    int    depth              = 1;
+
+    // I think this has something like O(n+log(n)) on a ballanced
+    // tree because I have to traverse back the rightmost leaf to
+    // the root to get a break condition.
+    while (node) {
+        if (previous == node->right) {
+            previous = node;
+            node     = node->parent;
+            depth--;
+            continue;
+        }
+
+        if ((NULL == node->left || previous == node->left)) {
+            cb(node->data, depth);
+            previous = node;
+
+            if (NULL != node->right) {
+                node = node->right;
+                depth++;
+            } else {
+                node = node->parent;
+                depth--;
+            }
+        } else {
+            previous = node;
+            node     = node->left;
+            depth++;
+        }
+    }
+}
+
+void printElement(int data, int depth)
+{
+    int  i;
+
+    for (i=0; i<depth-1; i++) printf("-");
+    printf("%02d(%02d)\n", data, depth);
+}
+
+/**
+ * =======================================================================
+ */
+int
+main(int argc, char * argv[])
+{
+    int              i;
+    struct element * root = NULL;
+
+    insertElement(&root, 13);
+    insertElement(&root, 8);
+    insertElement(&root, 16);
+    insertElement(&root, 11);
+    insertElement(&root, 3);
+    insertElement(&root, 9);
+    insertElement(&root, 12);
+    insertElement(&root, 10);
+
+    /*
+     * after this I have the following:
+     *
+     * Element 03: n=0x0xcf50d0 p=0x0xcf5040 l=0x(nil) r=0x(nil)
+     * Element 08: n=0x0xcf5040 p=0x0xcf5010 l=0x0xcf50d0 r=0x0xcf50a0
+     * Element 09: n=0x0xcf5100 p=0x0xcf50a0 l=0x(nil) r=0x0xcf5160
+     * Element 10: n=0x0xcf5160 p=0x0xcf5100 l=0x(nil) r=0x(nil)
+     * Element 11: n=0x0xcf50a0 p=0x0xcf5040 l=0x0xcf5100 r=0x0xcf5130
+     * Element 12: n=0x0xcf5130 p=0x0xcf50a0 l=0x(nil) r=0x(nil)
+     * Element 13: n=0x0xcf5010 p=0x(nil) l=0x0xcf5040 r=0x0xcf5070
+     * Element 16: n=0x0xcf5070 p=0x0xcf5010 l=0x(nil) r=0x(nil)
+     *
+     * which translates to:
+     * 
+     * 03 has p:08, l:N , R:N
+     * 08 has p:13, l:03, r:11
+     * 09 has p:11, l:N , r:10
+     * 10 has p:09, l:N , r:N
+     * 11 has p:08, l:09, r:12
+     * 12 has p:11, l:N , r:N
+     * 13 has p:N , l:08, r:16
+     * 16 has p:13, l:N , r:N
+     *                    
+     * which visualizes as:
+     *                      13
+     *           08                      16
+     *      03            11            0  0
+     *     0  0       09      12
+     *              0   10   0  0
+     *
+     * Looks like the insert works properly.
+     * So the problem is out traversing...
+     */
+    puts("elements:");
+    for (i=1; i<20; i++) {
+        struct element * element = findElement(root, i);
+        printf("Element %02d: n=0x%p p=0x%p l=0x%p r=0x%p\n",
+                i,
+                element,
+                element ? element->parent : 0x0,
+                element ? element->left : 0x0,
+                element ? element->right : 0x0);
+    }
+
+    puts("traverse");
+    traverse(root, printElement);
+
+    return 0;
+}
+
+// vim: set et ts=4 sw=4: