// solution for http://www.geeksforgeeks.org/sum-numbers-formed-root-leaf-paths/

TreeSum.java

package com.yekmer.geeksforgeeks;

class TreeSum {
	static TreeSum ts;
	static int sum = 0;
	
    public static void main(String[] args) {
    	ts = new TreeSum();
    	
    	Node l122 = ts.new Node(null, null, 4);
    	Node l121 = ts.new Node(null, null, 7);
    	Node r12 = ts.new Node(null, null, 4);
    	Node l12 = ts.new Node(l122, l121, 5);
    	Node l11 = ts.new Node(null, null, 2);
    	Node r1 = ts.new Node(r12, null, 5);
    	Node l1 = ts.new Node(l12, l11, 3);
    	Node root = ts.new Node(r1, l1, 6);
    	
    	int no = 0;
        dfs(root, no);
        
        System.out.println(sum);
    }
    
    public static void dfs(Node node, int number) {
        if(node == null) {
            return;
        }
        number = number * 10 + node.value;
        if(node.left == null && node.right == null) {
        	sum += number;
        } else {
            dfs(node.left, number);
            dfs(node.right, number);
        }
    }
    
    class Node {
    	
    	Node right;
        Node left;
        int value;
        
    	public Node(Node right, Node left, int value) {
    		this.right = right;
    		this.left = left;
    		this.value = value;
    	}
        
    }
}