How do I print out a tree structure?
The trick is to pass a string as the indent and to treat the last child specially:
class Node
{
public void PrintPretty(string indent, bool last)
{
Console.Write(indent);
if (last)
{
Console.Write("\\-");
indent += " ";
}
else
{
Console.Write("|-");
indent += "| ";
}
Console.WriteLine(Name);
for (int i = 0; i < Children.Count; i++)
Children[i].PrintPretty(indent, i == Children.Count - 1);
}
}
If called like this:
root.PrintPretty("", true);
will output in this style:
\-root
\-child
|-child
\-child
|-child
|-child
\-child
|-child
|-child
| |-child
| \-child
| |-child
| |-child
| |-child
| \-child
| \-child
| \-child
\-child
|-child
|-child
|-child
| \-child
\-child
\-child
Printing values in a tree structure in Java?
This approach runs into trouble because any calls to println() preclude printing further nodes on a line. Using a level order traversal/BFS will enable you to call println() to move to the next line only when all nodes on a given tree level have already been printed.
The bigger difficulty lies in keeping track of the horizontal placement of each node in a level. Doing this properly involves considering the depth, length of the node data and any empty children. If you can, consider printing your tree with depth increasing from left to right, similar to the unix command tree, rather than top-down, which simplifies the algorithm.
Here's a proof-of-concept for a top-down print. Spacing formulas are from this excellent post on this very topic. The strategy I used is to run a BFS using a queue, storing nodes (and null placeholders) in a list per level. Once the end of a level is reached, spacing is determined based on the number of nodes on a level, which is 2n-1, and printed. A simplifying assumption is that node data width is 1.
import java.util.*;
import static java.lang.System.out;
public class Main {
static void printLevelOrder(Node root) {
LinkedList<QItem> queue = new LinkedList<>();
ArrayList<Node> level = new ArrayList<>();
int depth = height(root);
queue.add(new QItem(root, depth));
for (;;) {
QItem curr = queue.poll();
if (curr.depth < depth) {
depth = curr.depth;
for (int i = (int)Math.pow(2, depth) - 1; i > 0; i--) {
out.print(" ");
}
for (Node n : level) {
out.print(n == null ? " " : n.val);
for (int i = (int)Math.pow(2, depth + 1); i > 1; i--) {
out.print(" ");
}
}
out.println();
level.clear();
if (curr.depth <= 0) {
break;
}
}
level.add(curr.node);
if (curr.node == null) {
queue.add(new QItem(null, depth - 1));
queue.add(new QItem(null, depth - 1));
}
else {
queue.add(new QItem(curr.node.left, depth - 1));
queue.add(new QItem(curr.node.right, depth - 1));
}
}
}
static int height(Node root) {
return root == null ? 0 : 1 + Math.max(
height(root.left), height(root.right)
);
}
public static void main(String[] args) {
printLevelOrder(
new Node<Integer>(
1,
new Node<Integer>(
2,
new Node<Integer>(
4,
new Node<Integer>(7, null, null),
new Node<Integer>(8, null, null)
),
null
),
new Node<Integer>(
3,
new Node<Integer>(
5,
new Node<Integer>(9, null, null),
null
),
new Node<Integer>(
6,
null,
new Node<Character>('a', null, null)
)
)
)
);
}
}
class Node<T> {
Node left;
Node right;
T val;
public Node(T val, Node left, Node right) {
this.left = left;
this.right = right;
this.val = val;
}
}
class QItem {
Node node;
int depth;
public QItem(Node node, int depth) {
this.node = node;
this.depth = depth;
}
}
Output:
1
2 3
4 5 6
7 8 9 a
Try it!
How to print binary tree diagram in Java?
I've created simple binary tree printer. You can use and modify it as you want, but it's not optimized anyway. I think that a lot of things can be improved here ;)
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class BTreePrinterTest {
private static Node<Integer> test1() {
Node<Integer> root = new Node<Integer>(2);
Node<Integer> n11 = new Node<Integer>(7);
Node<Integer> n12 = new Node<Integer>(5);
Node<Integer> n21 = new Node<Integer>(2);
Node<Integer> n22 = new Node<Integer>(6);
Node<Integer> n23 = new Node<Integer>(3);
Node<Integer> n24 = new Node<Integer>(6);
Node<Integer> n31 = new Node<Integer>(5);
Node<Integer> n32 = new Node<Integer>(8);
Node<Integer> n33 = new Node<Integer>(4);
Node<Integer> n34 = new Node<Integer>(5);
Node<Integer> n35 = new Node<Integer>(8);
Node<Integer> n36 = new Node<Integer>(4);
Node<Integer> n37 = new Node<Integer>(5);
Node<Integer> n38 = new Node<Integer>(8);
root.left = n11;
root.right = n12;
n11.left = n21;
n11.right = n22;
n12.left = n23;
n12.right = n24;
n21.left = n31;
n21.right = n32;
n22.left = n33;
n22.right = n34;
n23.left = n35;
n23.right = n36;
n24.left = n37;
n24.right = n38;
return root;
}
private static Node<Integer> test2() {
Node<Integer> root = new Node<Integer>(2);
Node<Integer> n11 = new Node<Integer>(7);
Node<Integer> n12 = new Node<Integer>(5);
Node<Integer> n21 = new Node<Integer>(2);
Node<Integer> n22 = new Node<Integer>(6);
Node<Integer> n23 = new Node<Integer>(9);
Node<Integer> n31 = new Node<Integer>(5);
Node<Integer> n32 = new Node<Integer>(8);
Node<Integer> n33 = new Node<Integer>(4);
root.left = n11;
root.right = n12;
n11.left = n21;
n11.right = n22;
n12.right = n23;
n22.left = n31;
n22.right = n32;
n23.left = n33;
return root;
}
public static void main(String[] args) {
BTreePrinter.printNode(test1());
BTreePrinter.printNode(test2());
}
}
class Node<T extends Comparable<?>> {
Node<T> left, right;
T data;
public Node(T data) {
this.data = data;
}
}
class BTreePrinter {
public static <T extends Comparable<?>> void printNode(Node<T> root) {
int maxLevel = BTreePrinter.maxLevel(root);
printNodeInternal(Collections.singletonList(root), 1, maxLevel);
}
private static <T extends Comparable<?>> void printNodeInternal(List<Node<T>> nodes, int level, int maxLevel) {
if (nodes.isEmpty() || BTreePrinter.isAllElementsNull(nodes))
return;
int floor = maxLevel - level;
int endgeLines = (int) Math.pow(2, (Math.max(floor - 1, 0)));
int firstSpaces = (int) Math.pow(2, (floor)) - 1;
int betweenSpaces = (int) Math.pow(2, (floor + 1)) - 1;
BTreePrinter.printWhitespaces(firstSpaces);
List<Node<T>> newNodes = new ArrayList<Node<T>>();
for (Node<T> node : nodes) {
if (node != null) {
System.out.print(node.data);
newNodes.add(node.left);
newNodes.add(node.right);
} else {
newNodes.add(null);
newNodes.add(null);
System.out.print(" ");
}
BTreePrinter.printWhitespaces(betweenSpaces);
}
System.out.println("");
for (int i = 1; i <= endgeLines; i++) {
for (int j = 0; j < nodes.size(); j++) {
BTreePrinter.printWhitespaces(firstSpaces - i);
if (nodes.get(j) == null) {
BTreePrinter.printWhitespaces(endgeLines + endgeLines + i + 1);
continue;
}
if (nodes.get(j).left != null)
System.out.print("/");
else
BTreePrinter.printWhitespaces(1);
BTreePrinter.printWhitespaces(i + i - 1);
if (nodes.get(j).right != null)
System.out.print("\\");
else
BTreePrinter.printWhitespaces(1);
BTreePrinter.printWhitespaces(endgeLines + endgeLines - i);
}
System.out.println("");
}
printNodeInternal(newNodes, level + 1, maxLevel);
}
private static void printWhitespaces(int count) {
for (int i = 0; i < count; i++)
System.out.print(" ");
}
private static <T extends Comparable<?>> int maxLevel(Node<T> node) {
if (node == null)
return 0;
return Math.max(BTreePrinter.maxLevel(node.left), BTreePrinter.maxLevel(node.right)) + 1;
}
private static <T> boolean isAllElementsNull(List<T> list) {
for (Object object : list) {
if (object != null)
return false;
}
return true;
}
}
Output 1 :
2
/ \
/ \
/ \
/ \
7 5
/ \ / \
/ \ / \
2 6 3 6
/ \ / \ / \ / \
5 8 4 5 8 4 5 8
Output 2 :
2
/ \
/ \
/ \
/ \
7 5
/ \ \
/ \ \
2 6 9
/ \ /
5 8 4
Printing a Tree data structure in Python
Yes, move the __repr__ code to __str__, then call str() on your tree or pass it to the print statement. Remember to use __str__ in the recursive calls too:
class node(object):
def __init__(self, value, children = []):
self.value = value
self.children = children
def __str__(self, level=0):
ret = "\t"*level+repr(self.value)+"\n"
for child in self.children:
ret += child.__str__(level+1)
return ret
def __repr__(self):
return '<tree node representation>'
Demo:
>>> root = node('grandmother')
>>> root.children = [node('daughter'), node('son')]
>>> root.children[0].children = [node('granddaughter'), node('grandson')]
>>> root.children[1].children = [node('granddaughter'), node('grandson')]
>>> root
<tree node representation>
>>> str(root)
"'grandmother'\n\t'daughter'\n\t\t'granddaughter'\n\t\t'grandson'\n\t'son'\n\t\t'granddaughter'\n\t\t'grandson'\n"
>>> print root
'grandmother'
'daughter'
'granddaughter'
'grandson'
'son'
'granddaughter'
'grandson'
Print binary tree in a pretty way using c++
Here is an example of code creating a text-based representation of a binary tree. This demonstration uses a minimally useful binary tree class (BinTree), with a small footprint, just to avoid bloating the example's size.
Its text-rendering member functions are more serious, using iteration rather than recursion, as found in other parts of the class.
This does its job in three steps, first a vector of rows of string values is put together.
Then this is used to format lines of text strings representing the tree.
Then the strings are cleaned up and dumped to cout.
As an added bonus, the demo includes a "random tree" feature, for hours of nonstop entertainment.
#include <iostream>
#include <vector>
#include <string>
#include <sstream>
#include <algorithm>
#include <random>
using std::vector;
using std::string;
using std::cout;
template <typename T>
class BinTree {
struct Node {
T value;
Node *left,*right;
Node() : left(nullptr),right(nullptr) {}
Node(const T& value) :value(value),left(nullptr),right(nullptr) {}
// stack-abusing recursion everywhere, for small code
~Node() { delete left; delete right; }
int max_depth() const {
const int left_depth = left ? left->max_depth() : 0;
const int right_depth = right ? right->max_depth() : 0;
return (left_depth > right_depth ? left_depth : right_depth) + 1;
}
};
Node *root;
public:
BinTree() : root(nullptr) {}
~BinTree() { delete root; }
int get_max_depth() const { return root ? root->max_depth() : 0; }
void clear() { delete root; root = nullptr; }
void insert() {}
template <typename ...Args>
void insert(const T& value, Args...more) {
if(!root) {
root = new Node(value);
} else {
Node* p = root;
for(;;) {
if(value == p->value) return;
Node* &pchild = value < p->value ? p->left : p->right;
if(!pchild) {
pchild = new Node(value);
break;
}
p = pchild;
}
}
insert(more...);
}
struct cell_display {
string valstr;
bool present;
cell_display() : present(false) {}
cell_display(std::string valstr) : valstr(valstr), present(true) {}
};
using display_rows = vector< vector< cell_display > >;
// The text tree generation code below is all iterative, to avoid stack faults.
// get_row_display builds a vector of vectors of cell_display structs
// each vector of cell_display structs represents one row, starting at the root
display_rows get_row_display() const {
// start off by traversing the tree to
// build a vector of vectors of Node pointers
vector<Node*> traversal_stack;
vector< std::vector<Node*> > rows;
if(!root) return display_rows();
Node *p = root;
const int max_depth = root->max_depth();
rows.resize(max_depth);
int depth = 0;
for(;;) {
// Max-depth Nodes are always a leaf or null
// This special case blocks deeper traversal
if(depth == max_depth-1) {
rows[depth].push_back(p);
if(depth == 0) break;
--depth;
continue;
}
// First visit to node? Go to left child.
if(traversal_stack.size() == depth) {
rows[depth].push_back(p);
traversal_stack.push_back(p);
if(p) p = p->left;
++depth;
continue;
}
// Odd child count? Go to right child.
if(rows[depth+1].size() % 2) {
p = traversal_stack.back();
if(p) p = p->right;
++depth;
continue;
}
// Time to leave if we get here
// Exit loop if this is the root
if(depth == 0) break;
traversal_stack.pop_back();
p = traversal_stack.back();
--depth;
}
// Use rows of Node pointers to populate rows of cell_display structs.
// All possible slots in the tree get a cell_display struct,
// so if there is no actual Node at a struct's location,
// its boolean "present" field is set to false.
// The struct also contains a string representation of
// its Node's value, created using a std::stringstream object.
display_rows rows_disp;
std::stringstream ss;
for(const auto& row : rows) {
rows_disp.emplace_back();
for(Node* pn : row) {
if(pn) {
ss << pn->value;
rows_disp.back().push_back(cell_display(ss.str()));
ss = std::stringstream();
} else {
rows_disp.back().push_back(cell_display());
} } }
return rows_disp;
}
// row_formatter takes the vector of rows of cell_display structs
// generated by get_row_display and formats it into a test representation
// as a vector of strings
vector<string> row_formatter(const display_rows& rows_disp) const {
using s_t = string::size_type;
// First find the maximum value string length and put it in cell_width
s_t cell_width = 0;
for(const auto& row_disp : rows_disp) {
for(const auto& cd : row_disp) {
if(cd.present && cd.valstr.length() > cell_width) {
cell_width = cd.valstr.length();
} } }
// make sure the cell_width is an odd number
if(cell_width % 2 == 0) ++cell_width;
// allows leaf nodes to be connected when they are
// all with size of a single character
if(cell_width < 3) cell_width = 3;
// formatted_rows will hold the results
vector<string> formatted_rows;
// some of these counting variables are related,
// so its should be possible to eliminate some of them.
s_t row_count = rows_disp.size();
// this row's element count, a power of two
s_t row_elem_count = 1 << (row_count-1);
// left_pad holds the number of space charactes at the beginning of the bottom row
s_t left_pad = 0;
// Work from the level of maximum depth, up to the root
// ("formatted_rows" will need to be reversed when done)
for(s_t r=0; r<row_count; ++r) {
const auto& cd_row = rows_disp[row_count-r-1]; // r reverse-indexes the row
// "space" will be the number of rows of slashes needed to get
// from this row to the next. It is also used to determine other
// text offsets.
s_t space = (s_t(1) << r) * (cell_width + 1) / 2 - 1;
// "row" holds the line of text currently being assembled
string row;
// iterate over each element in this row
for(s_t c=0; c<row_elem_count; ++c) {
// add padding, more when this is not the leftmost element
row += string(c ? left_pad*2+1 : left_pad, ' ');
if(cd_row[c].present) {
// This position corresponds to an existing Node
const string& valstr = cd_row[c].valstr;
// Try to pad the left and right sides of the value string
// with the same number of spaces. If padding requires an
// odd number of spaces, right-sided children get the longer
// padding on the right side, while left-sided children
// get it on the left side.
s_t long_padding = cell_width - valstr.length();
s_t short_padding = long_padding / 2;
long_padding -= short_padding;
row += string(c%2 ? short_padding : long_padding, ' ');
row += valstr;
row += string(c%2 ? long_padding : short_padding, ' ');
} else {
// This position is empty, Nodeless...
row += string(cell_width, ' ');
}
}
// A row of spaced-apart value strings is ready, add it to the result vector
formatted_rows.push_back(row);
// The root has been added, so this loop is finsished
if(row_elem_count == 1) break;
// Add rows of forward- and back- slash characters, spaced apart
// to "connect" two rows' Node value strings.
// The "space" variable counts the number of rows needed here.
s_t left_space = space + 1;
s_t right_space = space - 1;
for(s_t sr=0; sr<space; ++sr) {
string row;
for(s_t c=0; c<row_elem_count; ++c) {
if(c % 2 == 0) {
row += string(c ? left_space*2 + 1 : left_space, ' ');
row += cd_row[c].present ? '/' : ' ';
row += string(right_space + 1, ' ');
} else {
row += string(right_space, ' ');
row += cd_row[c].present ? '\\' : ' ';
}
}
formatted_rows.push_back(row);
++left_space;
--right_space;
}
left_pad += space + 1;
row_elem_count /= 2;
}
// Reverse the result, placing the root node at the beginning (top)
std::reverse(formatted_rows.begin(), formatted_rows.end());
return formatted_rows;
}
// Trims an equal number of space characters from
// the beginning of each string in the vector.
// At least one string in the vector will end up beginning
// with no space characters.
static void trim_rows_left(vector<string>& rows) {
if(!rows.size()) return;
auto min_space = rows.front().length();
for(const auto& row : rows) {
auto i = row.find_first_not_of(' ');
if(i==string::npos) i = row.length();
if(i == 0) return;
if(i < min_space) min_space = i;
}
for(auto& row : rows) {
row.erase(0, min_space);
} }
// Dumps a representation of the tree to cout
void Dump() const {
const int d = get_max_depth();
// If this tree is empty, tell someone
if(d == 0) {
cout << " <empty tree>\n";
return;
}
// This tree is not empty, so get a list of node values...
const auto rows_disp = get_row_display();
// then format these into a text representation...
auto formatted_rows = row_formatter(rows_disp);
// then trim excess space characters from the left sides of the text...
trim_rows_left(formatted_rows);
// then dump the text to cout.
for(const auto& row : formatted_rows) {
std::cout << ' ' << row << '\n';
}
}
};
int main() {
BinTree<int> bt;
// Build OP's tree
bt.insert(8,5,2,6,10,9,11);
cout << "Tree from OP:\n\n";
bt.Dump();
cout << "\n\n";
bt.clear();
// Build a random tree
// This toy tree can't balance, so random
// trees often look more like linked lists.
// Just keep trying until a nice one shows up.
std::random_device rd;
std::mt19937 rng(rd());
int MaxCount=20;
int MaxDepth=5;
const int Min=0, Max=1000;
std::uniform_int_distribution<int> dist(Min,Max);
while(MaxCount--) {
bt.insert(dist(rng));
if(bt.get_max_depth() >= MaxDepth) break;
}
cout << "Randomly generated tree:\n\n";
bt.Dump();
}
An example of the output:
Tree from OP:
8
/ \
/ \
/ \
5 10
/ \ / \
2 6 9 11
Randomly generated tree:
703
/ \
/ \
/ \
/ \
/ \
/ \
/ \
/ \
/ \
/ \
/ \
/ \
/ \
/ \
/ \
137 965
/ \ /
/ \ /
/ \ /
/ \ /
/ \ /
/ \ /
/ \ /
41 387 786
\ / \ / \
\ / \ / \
\ / \ / \
95 382 630 726 813
\
841
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