From 0233e876c40c5e9f1ecebaa9357851df35c176ea Mon Sep 17 00:00:00 2001
From: inex <gitea@inex.rocks>
Date: Thu, 21 May 2020 05:59:52 +0300
Subject: [PATCH] Task 5, closes #5

---
 task5/task5.c | 152 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 152 insertions(+)
 create mode 100644 task5/task5.c

diff --git a/task5/task5.c b/task5/task5.c
new file mode 100644
index 0000000..0a85385
--- /dev/null
+++ b/task5/task5.c
@@ -0,0 +1,152 @@
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct bstree {
+  int key;
+  char *value;
+
+  struct bstree *left;
+  struct bstree *right;
+} TREE_NODE;
+
+TREE_NODE *tree_create(int key, char *value) {
+  TREE_NODE *node;
+  node = malloc(sizeof(TREE_NODE));
+  if (node == NULL) {
+    fprintf(stderr, "Error allocating node");
+    return NULL;
+  }
+  node->key = key;
+  node->value = value;
+  node->left = NULL;
+  node->right = NULL;
+  return node;
+}
+
+void add_leaf(int key, char *value, TREE_NODE *tree) {
+  TREE_NODE *node;
+  node = tree_create(key, value);
+  if (tree == NULL) {
+    return;
+  }
+
+  while (tree != NULL) {
+    if (key < tree->key) {
+      if (tree->left == NULL) {
+        tree->left = node;
+        return;
+      } else {
+        tree = tree->left;
+      }
+    } else if (key > tree->key) {
+      if (tree->right == NULL) {
+        tree->right = node;
+        return;
+      } else {
+        tree = tree->right;
+      }
+    } else
+      return;
+  }
+}
+
+TREE_NODE *tree_lookup(TREE_NODE *tree, int key) {
+  while (tree != NULL) {
+    if (key == tree->key) {
+      return tree;
+    } else if (key < tree->key) {
+      tree = tree->left;
+    } else {
+      tree = tree->right;
+    }
+  }
+  return tree;
+}
+
+TREE_NODE *parent_lookup(TREE_NODE *tree, int key) {
+  while (tree != NULL) {
+    if ((tree->left != NULL && (key == (tree->left)->key)) ||
+        (tree->right != NULL && (key == (tree->right)->key))) {
+      return tree;
+    } else if (key < tree->key) {
+      tree = tree->left;
+    } else {
+      tree = tree->right;
+    }
+  }
+  return tree;
+}
+
+void delete_node(TREE_NODE *tree, int key) {
+
+  TREE_NODE *node = tree_lookup(tree, key);
+  tree = parent_lookup(tree, key);
+
+  if (node->left == NULL && node->right == NULL) {
+    if (tree->left == node) {
+      free(node);
+      tree->left = NULL;
+    } else {
+      free(node);
+      tree->right = NULL;
+    }
+  } else if (node->left != NULL && node->right == NULL) {
+    if (tree->left == node) {
+      tree->left = node->left;
+      free(node);
+    } else {
+      tree->right = node->left;
+      free(node);
+    }
+  } else if (node->left == NULL && node->right != NULL) {
+    if (tree->left == node) {
+      tree->left = node->right;
+      free(node);
+    } else {
+      tree->right = node->right;
+      free(node);
+    }
+  } else {
+    if ((node->right)->left == NULL) {
+      tree = node->right;
+      node->key = tree->key;
+      node->value = tree->value;
+      node->right = tree->right;
+      free(tree);
+    } else {
+      tree = node;
+      while (tree->left != NULL) {
+        tree = tree->left;
+      }
+      node->key = tree->key;
+      node->value = tree->value;
+      free(tree);
+    }
+  }
+  return;
+}
+
+int main(int argc, char const *argv[]) {
+  TREE_NODE *tree;
+  tree = tree_create(180, "First");
+  add_leaf(50, "second", tree);
+  add_leaf(250, "third", tree);
+  add_leaf(40, "fourth", tree);
+  add_leaf(30, "fifth", tree);
+  add_leaf(45, "sixth", tree);
+  add_leaf(44, "seventh", tree);
+  delete_node(tree, 45);
+  return 0;
+}
+/*
+                180
+              /    \
+            50      250
+          /
+        40
+      /    \
+    30     45
+         /
+        44
+*/