print all paths from root to leaf in a binary tree in java

Table of Contents

- Algorithm:

Java Binary tree tutorial:

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This is 9th part of java binary tree tutorial.

In this post, we will see about program to print all paths from root to leaf in a binary tree in java.
Below diagram will show all paths from root to leaf:

Algorithm:

Steps for print all paths from root to leaf are:

If node is null then return 0
put node.data in array and increment len by 1.
If encounterd leaf node(i.e. node.left is null and node.right is null) then print array.
Recursively visit left subtree and right subtree

Code for recursion will be:


// Prints all paths to leaf
 public static void printAllPathsToLeaf(TreeNode node, int[] path, int len) {
     if ( node == null )
         return;

     // storing data in array
     path[len] = node.data;
     len++;

     if(node.left == null && node.right == null) {
         // leaf node is reached
         printArray(path,len);
         return;
     }

     printAllPathsToLeaf(node.left, path, len);
     printAllPathsToLeaf(node.right, path, len);
 }

// Prints all paths to leaf

public static void printAllPathsToLeaf(TreeNode node, int[] path, int len) {

if ( node == null )

return;

// storing data in array

path[len] = node.data;

len++;

if(node.left == null && node.right == null) {

// leaf node is reached

printArray(path,len);

return;

}

printAllPathsToLeaf(node.left, path, len);

printAllPathsToLeaf(node.right, path, len);

}

Lets create java program for counting number of leaf nodes:


package org.arpit.java2blog.binarytree;

public class BinaryTreePrintAllPaths {

    public static class TreeNode
    {
        int data;
        TreeNode left;
        TreeNode right;
        TreeNode(int data)
        {
            this.data=data;
        }
    }

    // Prints all paths to leaf
    public static void printAllPathsToLeaf(TreeNode node, int[] path, int len) {
        if ( node == null )
            return;

        // storing data in array
        path[len] = node.data;
        len++;

        if(node.left == null && node.right == null) {
            // leaf node is reached
            printArray(path,len);
            return;
        }

        printAllPathsToLeaf(node.left, path, len);
        printAllPathsToLeaf(node.right, path, len);
    }

    public static void main(String[] args)
    {
        // Creating a binary tree
        TreeNode rootNode=createBinaryTree();
        System.out.println("Printing all paths from root to leaf :");
        printAllPathsToLeaf(rootNode,new int[1000],0);
    }

    public static void  printArray(int[] path,int len)
    {
        for (int i = 0; i < len; i++) {
            System.out.print(" "+path[i]);
        }
        System.out.println();
    }
    public static TreeNode createBinaryTree()
    {

        TreeNode rootNode =new TreeNode(40);
        TreeNode node20=new TreeNode(20);
        TreeNode node10=new TreeNode(10);
        TreeNode node30=new TreeNode(30);
        TreeNode node60=new TreeNode(60);
        TreeNode node50=new TreeNode(50);
        TreeNode node70=new TreeNode(70);
        TreeNode node5=new TreeNode(5);
        TreeNode node55=new TreeNode(55);

        rootNode.left=node20;
        rootNode.right=node60;

        node20.left=node10;
        node20.right=node30;

        node60.left=node50;
        node60.right=node70;
        node10.left=node5;
        node50.right=node55;

        return rootNode;
    }
}

package org.arpit.java2blog.binarytree;

public class BinaryTreePrintAllPaths {

public static class TreeNode

{

int data;

TreeNode left;

TreeNode right;

TreeNode(int data)

{

this.data=data;

}

// Prints all paths to leaf

public static void printAllPathsToLeaf(TreeNode node, int[] path, int len) {

if ( node == null )

return;

// storing data in array

path[len] = node.data;

len++;

if(node.left == null && node.right == null) {

// leaf node is reached

printArray(path,len);

return;

}

printAllPathsToLeaf(node.left, path, len);

printAllPathsToLeaf(node.right, path, len);

}

public static void main(String[] args)

{

// Creating a binary tree

TreeNode rootNode=createBinaryTree();

System.out.println("Printing all paths from root to leaf :");

printAllPathsToLeaf(rootNode,new int[1000],0);

}

public static void printArray(int[] path,int len)

{

for (int i = 0; i < len; i++) {

System.out.print(" "+path[i]);

}

System.out.println();

}

public static TreeNode createBinaryTree()

{

TreeNode rootNode =new TreeNode(40);

TreeNode node20=new TreeNode(20);

TreeNode node10=new TreeNode(10);

TreeNode node30=new TreeNode(30);

TreeNode node60=new TreeNode(60);

TreeNode node50=new TreeNode(50);

TreeNode node70=new TreeNode(70);

TreeNode node5=new TreeNode(5);

TreeNode node55=new TreeNode(55);

rootNode.left=node20;

rootNode.right=node60;

node20.left=node10;

node20.right=node30;

node60.left=node50;

node60.right=node70;

node10.left=node5;

node50.right=node55;

return rootNode;

}

Run above program and you will get following output:


Printing all paths from root to leaf :
40 20 10 5
40 20 30
40 60 50 55
40 60 70

Printing all paths from root to leaf :

40 20 10 5

40 20 30

40 60 50 55

40 60 70

Java Binary tree tutorial:

Please go through java interview programs for more such programs.

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Comments

John Williams says:

May 2, 2015 at 8:22 pm

I appreciate your blog. Its really nice on java programming. Its a great tutorial for the beginners. Really liked it. Thank you for all the information.

tanu says:

June 2, 2015 at 7:14 pm

hi
can u plz help me
actually this following part of your code is not working, giving an error
plz resolve this
•if(node.left == null && node.right == null) {
• // leaf node is reached
• printArray(path,len);
• return;
• }
•
thanks
Read more at https://www.java2blog.com/2014/08/print-all-paths-…

1. arpitmandliya says:
  
  June 24, 2015 at 6:11 pm
  
  Thanks Tanu for pointing out. I have updated the code