Dont know where to start?

#1

Can you please share the code regarding how to start about how to take inputs or do we have to make our own tree class??

#2

hey @bhavik911
I think the generic tree will be added to your course

#3

it is added.
But I don’t how to get input like this

#4

I mean using the integers given

#5

exactlly generic tree , no of children will not exceed 2.

#6

No i mean I dont understand how to take input in that we used true and false , should i use loop here?

#7

@bhavik911
use loop here

#8 
package Trees;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Scanner;

public class SumAtLevelK {
    static Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) {

        BT tree = new BT();
        int k = scanner.nextInt();
        System.out.println(tree.sumK(k));


    }

    static class BT {
        private Node root;

        private class Node {
            int data;
            ArrayList<Node> children;

            public Node() {
                children = new ArrayList<>();
            }

            public Node(int data) {
                this.data = data;
                children = new ArrayList<>();
            }
        }

        public BT() {

            root = construct(null, -1);
        }


        private Node construct(Node parent, int ith) {
            //root

            //input
            int item = scanner.nextInt();
            //New node
            Node nn = new Node(item);
            //Enter no of child
            int no_of_child = scanner.nextInt();
            for (int i = 0; i < no_of_child; i++) {
                Node child = construct(nn, i);
                nn.children.add(child);
            }

            return nn;

        }

        public void display() {
            System.out.println("-------------");
            display(root);
            System.out.println("-------------");
        }

        private void display(Node node) {
            String str = node.data + "-> ";
            for (Node child : node.children) {
                str += child.data + " ";
            }
            str += ".";
            System.out.println(str);

            for (Node child : node.children) {
                display(child);
            }
        }

        public int sumK(int k) {
            return sumK(root, k);
        }

        private int sumK(Node root, int k) {
            LinkedList<Node> ll = new LinkedList<>();
            ll.add(root);
            int count = 0;
            int sum = 0;
            while (count <= k && !ll.isEmpty()) {
                Node rv = ll.removeFirst();
                if (count == k) {
                    sum += rv.data;
                    while (!ll.isEmpty()) {
                        Node sv = ll.removeFirst();
                        sum += sv.data;
                    }
                    return sum;
                }
                if (rv.children.size() != 0) {
                    count+=1;
                    for (int i = 0; i < rv.children.size(); i++)
                        ll.addLast(rv.children.get(i));
                }
            }
            return sum;
        }

    }
}

Can you tell tell whats the error here , the answer is not right

#9

you are doing wrong
debug your code for custom input :
sum at level 2
Here the tree looks like

                     1                                 Level 0
                /          \
              2              5                         Level 1
           /      \       /     \
          3       4      6        7                    Level 2

You are adding 5 3 and 4
it is simple recursion based Question

#10

What should be the change in my code , i dont get it?

#11

please reply what should i change?

#12

Logic is not correct .
it is simple to try recursive solution

#13

Hey , What should be the right logic for it , I am usimg queues but not able to get the right logic I think

#14

static int sum = 0;

private void SumAtLevel(Node node, int level, int cl) { // level is k and cl is current level
if (cl == level) {
sum += node.data;
}
for (Node Child : node.children) {
SumAtLevel(Child, level, cl + 1);
}

}
#15

Hey but taking a static variable isnt always a preferred option , as it was mentioned in the video, How should I do it without this

#16 
public int SumAtLevel(int level) {
return	SumAtLevel(this.root, level, 0);

}

private int SumAtLevel(Node node, int level, int cl) {
int sum=0;
if (cl == level) {
sum += node.data;
}

	for (Node Child : node.children) {
        sum +=SumAtLevel(Child, level, cl + 1);
	}
    return sum;

}