Question

For the below code, I’m getting the following error:

SearchTree.java:19: error: 'void' type not allowed here
  this.setRoot(this.insertgt(this.insertionSort(value)));

What’s the problem?

Code:

import java.util.Arrays;

public class SearchTree {
    private TreeNode root;
    private static int sum = 0;
    public void setRoot(TreeNode n){
        this.root = n;  
    }

    public TreeNode getRoot(){
        return this.root;   
    }

    // returns a SearchTree
    public void insert(int[] value) {
        System.out.println(value == null);
        this.setRoot(this.insertgt(this.insertionSort(value)));
    }

    public void insertgt(int[] value) {
        if (value.length == 0) return;
        TreeNode currentNode;
        currentNode.left = new TreeNode(ArrayMinimum.minimum(value));
        if (value.length > 0) {
            currentNode = new TreeNode(insertgt(value));
            currentNode.right = new TreeNode(insertgt(value));
        }
        return currentNode;
    }

    // returns sum of node.values
    public int sum() {
        if (this.left == null && this.right == null) return sum;
        sum = this.value + sum;
        if (this.left != null && this.right != null) {
            sum = this.left.sum();
            sum = this.right.sum();
        }
    }

    // returns number of nodes
    public int numberOfLeafs() {
        if (this.left == null && this.right == null)
            return(1 + this.left.numberOfLeafs() + this.right.numberOfLeafs());
        return(1 + this.left.numberOfLeafs() + this.right.numberOfLeafs() );
    }   

    // returns zahl if searchTree contains zahl
    public int search(int zahl) {
        if (this.value == zahl) return null;
        return(1 + this.left.search(zahl) + this.right.search(zahl));
    }   

    public int[] insertionSort(int[] data) {
        for(int i = 1; i < data.length; i++) {
            int t = data[i];
            int j = i - 1;
            while(j >= 0 && data[j] > t) {
                data[j + 1] = data[j];
                j--;
            }
            data[j + 1] = t;
        }
        return data;
    }   
}

class ArrayMinimum {
    // removes and returns the minimum element
    static int minimum(int [] v) {
        int min = v[0]; 
        for (int i = 0; i < v.length; i++) {
            if (v[i] < min) {
                min = v[i];
            }
        }
        ArrayUtils.remove(value, min);
        return min;
    }
}

Answer 1

The method setRoot expects to receive a TreeNode as a parameter, and the problem is that you are passing as a parameter the result of the method insertgt that is void, you would have to return a TreeNode object from the insertgt method

this.setRoot(this.insertgt(this.insertionSort(value)));