Construct Binary Tree from Preorder and Inorder Traversal

Construct Binary Tree from Preorder and Inorder Traversal

Given two integer arrays preorder and inorder where preorder is the preorder traversal of a binary tree and inorder is the inorder traversal of the same tree, construct and return the binary tree.

int preOrder_Index = 0;
    private void constructABinaryTree(Node node, int[] inorder_traversal, int[] preOrder_traversal) {
        Map<Integer,Integer> mp = new HashMap<>();
        for (int i=0; i < inorder_traversal.length; i++) {
            mp.put(inorder_traversal[i], i);
        } 
     subTree(preOrder_traversal, 0, preOrder_traversal.length, mp);
    }

    private Node subTree(int[] preOrder, int left, int right, Map<Integer, Integer> mp) {

        if(left > right) {
            return null;  //cant create a tree with left being less and right being more
        }
        Node root = new Node(preOrder[preOrder_Index++], null, null);
        root.left = subTree(preOrder, 0, mp.get(root.val), mp);
        root.right = subTree(preOrder, mp.get(root.val), right, mp);

        return root;
    }