A Simple Application which demonstrates how to pretty print a tree

prettyPrint.c

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

struct _Node;

typedef struct _Node Node;

struct _Node
{
	int value;
	Node* leftTree;
	Node* rightTree;
	Node* parent;
};

typedef Node* Tree;

Node* createNode(int val)
{
	Node* pNode = (Node*)malloc(sizeof(Node));
	pNode->value = val;
	pNode->leftTree = NULL;
	pNode->rightTree = NULL;
	pNode->parent = NULL;
	return pNode;
}

Tree AddValue(Tree t, int val)
{
	if (t == NULL)
	{
		return createNode(val);
	}
	
	Node* pNewNode = createNode(val);
	
	if (pNewNode->value <= t->value) 
	{
		if (t->leftTree == NULL)
		{
			t->leftTree = createNode(val);
			t->leftTree->parent = t;
		}
		else AddValue(t->leftTree, val);
	}
	else
	{
		if (t->rightTree == NULL)
		{
			t->rightTree = createNode(val);
			t->rightTree->parent = t;
		}
		else AddValue(t->rightTree, val);
	}
	
	return t;
}

int GetHeight(Tree tree)
{
	if (tree == NULL) return -1;
	int height = 0;
	if (tree->leftTree != NULL) height = 1 + GetHeight(tree->leftTree);
	if (tree->rightTree != NULL)
	{
		int rightHeight = 1 + GetHeight(tree->rightTree);
		height = rightHeight > height ? rightHeight : height;
	}
	return height;
}	

int NumOfDigits(int n)
{
	char str[10];
	sprintf(str, "%d\0", n);
	return strlen(str);
}

int GetWidth(Tree tree)
{
	if (tree == NULL) return 0;
	return NumOfDigits(tree->value) + GetWidth(tree->leftTree) + GetWidth(tree->rightTree);
}

void PrettyPrintRootOnLine(char** lines, int curHeight, Node* root, int start)
{
	if (root == NULL) return;

	char* line = lines[curHeight];

	int wordWidth = NumOfDigits(root->value);
	int wordStart = start + GetWidth(root->leftTree);
	int wordEnd = wordStart + wordWidth - 1;
	int end = wordEnd + GetWidth(root->rightTree);

	int i;
	int tempVal = root->value;
	for (i = wordEnd; i >= wordStart; i--)
	{
		line[i] = tempVal % 10 + '0';
		tempVal /= 10;
	}


	PrettyPrintRootOnLine(lines, curHeight + 1, root->leftTree, start);
	PrettyPrintRootOnLine(lines, curHeight + 1, root->rightTree, wordEnd + 1);
}

void PrettyPrint(Tree tree)
{
	int height = GetHeight(tree);
	int width = GetWidth(tree);
	char** lines;
	lines = (char**)malloc((height + 1) * sizeof(char*));
	int i;
	for (i = 0; i <= height; i++)
	{
		lines[i] = (char*)malloc((width + 1) * sizeof(char));
		int charNo;
		for (charNo = 0; charNo < width; charNo++)
		{
			lines[i][charNo] = ' ';
		}
		lines[i][width] = '\0';
	}
	
	PrettyPrintRootOnLine(lines, 0, tree, 0);
	
	for (i = 0; i <= height; i++) printf("%s\n", lines[i]);
}



int main()
{
	Tree t = NULL;
	
	t = AddValue(t, 5);
	AddValue(t, 3);
	AddValue(t, 20);
	AddValue(t, 2);
	AddValue(t, 1);
	AddValue(t, 16);
	AddValue(t, 18);
	AddValue(t, 9);
	AddValue(t, 14);
	
	PrettyPrint(t);
	
	return 0;
}