icp/oer/courses/c-advanced/sections/01-introduction/06-tree/solution.c

#include <stdio.h>
#include <stdlib.h>

typedef struct node
{
	int Value;
	struct node *Left;
	struct node *Right;
}node;

node *alloc_node(int Value, node *Left, node *Right)
{
  	node *NewNode = malloc(sizeof(node));
  	NewNode->Value = Value;
  	NewNode->Left = Left;
	NewNode->Right = Right;
      
	return NewNode;
}

// inserts into the right place in the tree
void tree_insert(node **Root, int Value)
{
	// TODO: implement this
	if(*Root)
	{
		node *Node = *Root;
		if(Value <= Node->Value)
		{
			tree_insert(&Node->Left, Value);
		}
	        else
		{
			tree_insert(&Node->Right, Value);
		}

	}
	else
	{
		*Root = alloc_node(Value, 0, 0);
	}
}

// finds the node with the given value.
// if it doesn't find one return null
node *tree_find(node *Root, int Value)
{
	// TODO: implement this
	node *Node = Root;
	if(Node)
	{
		if(Value < Node->Value)
		{
			tree_find(Node->Left, Value);
		}
	        else if(Value > Node->Value)
		{
			tree_find(Node->Right, Value);
		}
		else
		{
			return Node;
		}
	}
	return 0;
}

// deletes the node with the value while remaining sorted
void tree_delete(node **Root, node *Parent, int Value)
{
	node *Node = *Root;
	if(Node)
	{
		if(Value < Node->Value)
		{
			tree_delete(&Node->Left, Node, Value);
		}
	        else if(Value > Node->Value)
		{
			tree_delete(&Node->Right, Node, Value);
		}
		else // Found node
		{
			node *NodeToDelete = Node;
			if(NodeToDelete->Left && NodeToDelete->Right)
			{
				node *RightSubTree = NodeToDelete->Right;
				if(RightSubTree)
				{
					node *LowestNode = RightSubTree->Left;
					node *Prev;
					while(LowestNode->Left)
					{
						Prev = LowestNode;
						LowestNode = LowestNode->Left;
					}
					NodeToDelete->Value = LowestNode->Value;
					Prev->Left = 0;
					tree_delete(&LowestNode, Prev, LowestNode->Value);
				}
			}
			else if(NodeToDelete->Left)
			{
				if(Parent)
					Parent->Left = NodeToDelete->Left;
				free(NodeToDelete);
			}
			else if(NodeToDelete->Right)
			{
				if(Parent)
					Parent->Left = NodeToDelete->Right;
				free(NodeToDelete);
			}
			else
			{
				if(Parent)
					Parent->Left = 0;
				free(NodeToDelete);
			}
		}
	}
	
	// TODO: implement this
}

// prints every member in a sorted way
void tree_print_sorted(node *Root)
{
	// TODO: implement this
	node *Node = Root;
	if(Node)
	{
		node *Left = Node->Left;
		tree_print_sorted(Left);
		printf("%d ", Node->Value);
		node *Right = Node->Right;
		tree_print_sorted(Right);
	}
}

int main(int argc, char **argv)
{
	node *Root;
	int Numbers[10] = {9, 128, 3, 1, 42, 9001, 7, 500, 6, 10};

	// NOTE: filling the tree with numbers
	for(int i = 0 ; i < 10; i++)
	{
		tree_insert(&Root, Numbers[i]);
	}

	node *Nine = tree_find(Root, 9);
	int FoundNine = 0;
	if(Nine)
	{
		FoundNine = 1;
		node *Left = Nine->Left;
		node *Right = Nine->Right;
		printf("Found %d with direct child %d and %d\n", Nine->Value, (Left)? Left->Value: 0, (Right)? Right->Value : 0);
	}
	tree_delete(&Root, 0, 9);
	Nine = tree_find(Root, 9);
	if(Nine)
	{
		printf("Failed to delete %d\n", Nine->Value);
	}
	else
	{
		if(FoundNine)
			printf("Succesfully deleted 9\n");
	}

	tree_print_sorted(Root);
	printf("\n");
	
}