Here we are not going to discuss what binary trees are (please refer **this**, if you are looking for binary search trees), or their operations but printing them in ascii.

The below routine prints tree in ascii for a given Tree representation which contains list of nodes, and node structure is this

struct Tree
{
Tree * left, * right;
int element;
};

This pic illustrates what the below routine does on canvas..

Here is the printing routine..

//prints ascii tree for given Tree structure
void print_ascii_tree(Tree * t)
{
asciinode *proot;
int xmin, i;
if (t == NULL) return;
proot = build_ascii_tree(t);
compute_edge_lengths(proot);
for (i=0; iheight && i < MAX_HEIGHT; i++)
{
lprofile[i] = INFINITY;
}
compute_lprofile(proot, 0, 0);
xmin = 0;
for (i = 0; i height && i < MAX_HEIGHT; i++)
{
xmin = MIN(xmin, lprofile[i]);
}
for (i = 0; i height; i++)
{
print_next = 0;
print_level(proot, -xmin, i);
printf("\n");
}
if (proot->height >= MAX_HEIGHT)
{
printf("(This tree is taller than %d, and may be drawn incorrectly.)\n",
MAX_HEIGHT);
}
free_ascii_tree(proot);
}

Auxiliary routines..

//This function prints the given level of the given tree, assuming
//that the node has the given x cordinate.
void print_level(asciinode *node, int x, int level)
{
int i, isleft;
if (node == NULL) return;
isleft = (node->parent_dir == -1);
if (level == 0)
{
for (i=0; ilablen-isleft)/2)); i++)
{
printf(" ");
}
print_next += i;
printf("%s", node->label);
print_next += node->lablen;
}
else if (node->edge_length >= level)
{
if (node->left != NULL)
{
for (i=0; iright != NULL)
{
for (i=0; ileft,
x-node->edge_length-1,
level-node->edge_length-1);
print_level(node->right,
x+node->edge_length+1,
level-node->edge_length-1);
}
}
//This function fills in the edge_length and
//height fields of the specified tree
void compute_edge_lengths(asciinode *node)
{
int h, hmin, i, delta;
if (node == NULL) return;
compute_edge_lengths(node->left);
compute_edge_lengths(node->right);
/* first fill in the edge_length of node */
if (node->right == NULL && node->left == NULL)
{
node->edge_length = 0;
}
else
{
if (node->left != NULL)
{
for (i=0; ileft->height && i left, 0, 0);
hmin = node->left->height;
}
else
{
hmin = 0;
}
if (node->right != NULL)
{
for (i=0; iright->height && i right, 0, 0);
hmin = MIN(node->right->height, hmin);
}
else
{
hmin = 0;
}
delta = 4;
for (i=0; ileft != NULL && node->left->height == 1) ||
(node->right != NULL && node->right->height == 1))&&delta>4)
{
delta--;
}
node->edge_length = ((delta+1)/2) - 1;
}
//now fill in the height of node
h = 1;
if (node->left != NULL)
{
h = MAX(node->left->height + node->edge_length + 1, h);
}
if (node->right != NULL)
{
h = MAX(node->right->height + node->edge_length + 1, h);
}
node->height = h;
}

asciinode * build_ascii_tree_recursive(Tree * t)
{
asciinode * node;
if (t == NULL) return NULL;
node = malloc(sizeof(asciinode));
node->left = build_ascii_tree_recursive(t->left);
node->right = build_ascii_tree_recursive(t->right);
if (node->left != NULL)
{
node->left->parent_dir = -1;
}
if (node->right != NULL)
{
node->right->parent_dir = 1;
}
sprintf(node->label, "%d", t->element);
node->lablen = strlen(node->label);
return node;
}
//Copy the tree into the ascii node structre
asciinode * build_ascii_tree(Tree * t)
{
asciinode *node;
if (t == NULL) return NULL;
node = build_ascii_tree_recursive(t);
node->parent_dir = 0;
return node;
}
//Free all the nodes of the given tree
void free_ascii_tree(asciinode *node)
{
if (node == NULL) return;
free_ascii_tree(node->left);
free_ascii_tree(node->right);
free(node);
}
//The following function fills in the lprofile array for the given tree.
//It assumes that the center of the label of the root of this tree
//is located at a position (x,y). It assumes that the edge_length
//fields have been computed for this tree.
void compute_lprofile(asciinode *node, int x, int y)
{
int i, isleft;
if (node == NULL) return;
isleft = (node->parent_dir == -1);
lprofile[y] = MIN(lprofile[y], x-((node->lablen-isleft)/2));
if (node->left != NULL)
{
for (i=1; i edge_length && y+i left, x-node->edge_length-1, y+node->edge_length+1);
compute_lprofile(node->right, x+node->edge_length+1, y+node->edge_length+1);
}
void compute_rprofile(asciinode *node, int x, int y)
{
int i, notleft;
if (node == NULL) return;
notleft = (node->parent_dir != -1);
rprofile[y] = MAX(rprofile[y], x+((node->lablen-notleft)/2));
if (node->right != NULL)
{
for (i=1; i edge_length && y+i left, x-node->edge_length-1, y+node->edge_length+1);
compute_rprofile(node->right, x+node->edge_length+1, y+node->edge_length+1);
}

Here is the asciii tree structure…

struct asciinode_struct
{
asciinode * left, * right;
//length of the edge from this node to its children
int edge_length;
int height;
int lablen;
//-1=I am left, 0=I am root, 1=right
int parent_dir;
//max supported unit32 in dec, 10 digits max
char label[11];
};

Please refer reference code for collection of posts in data structures

[note: I’d used msvc6 (which is a bit old one), so when you use new compilers you may get few compilations errors, fix them yourself or drop a msg over here..]