'LC 114. Flatten Binary Tree to Linked List Question

For the LC question here, I am struggling to find where I am going wrong with the recursive approach. I am able to do this problem iteratively, but I am not sure where I am going wrong with the recursive approach. If I can get some guidance, I would appreciate it

Iterative Solution (passes):

class Solution {
    public void flatten(TreeNode root) {
        List<Integer> preorderList = new ArrayList<>();
        preorder(root, preorderList);
        TreeNode flat = root;
        for (int i = 1; i < preorderList.size(); i++) {
            flat.left = null;
            flat.right = new TreeNode(preorderList.get(i));
            flat = flat.right;
        }
    }
    
    public void preorder(TreeNode root, List<Integer> list) {
        if (root == null) {
            return;
        }
        list.add(root.val);
        preorder(root.left, list);
        preorder(root.right, list);
    }
}

Recursive Solution (fails):

class Solution {
    public void flatten(TreeNode root) {
        List<Integer> preorderList = new ArrayList<>();
        preorder(root, preorderList);
        int[] idx = new int[1];
        flat = build(preorderList, idx);
    }
    
    public TreeNode build(List<Integer> list, int[] idx) {
        if (idx[0] == list.size()) {
            return null;
        }
        TreeNode root = new TreeNode(list.get(idx[0]));
        idx[0] += 1;        
        root.right = build(list, idx);
        root.left = null;
        return root;
    }
    
    public void preorder(TreeNode root, List<Integer> list) {
        if (root == null) {
            return;
        }
        list.add(root.val);
        preorder(root.left, list);
        preorder(root.right, list);
    }
}
javarecursionpythonif-statementsyntax


Solution 1:[1]

Your last 2 print statements are missing a closing ')'

import random
name = input("Please enter your name")
print(name)
integ = int(input(name + ","  +  " please enter an integer: "))
print(integ)
integ2 = int(input(name + "," + " please enter another integer: "))
print(integ2)
divis = (integ % integ2)
print(divis)
if divis == 0:
    print(str(integ) + " is divisible by " + (str(integ2)))
else:
    print(str(integ) + " is NOT divisible by " + (str(integ2)))

Solution 2:[2]

You have forgotten to close the brackets. It should be like this:

import random
name = input("Please enter your name")
print(name)
integ = int(input(name + ","  +  " please enter an integer: "))
print(integ)
integ2 = int(input(name + "," + " please enter another integer: "))
print(integ2)
divis = (integ % integ2)
print(divis)
if divis == 0:
    print(str(integ) + " is divisible by " + (str(integ2)))
else:
    print(str(integ) + " is NOT divisible by " + (str(integ2)))

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Meny Issakov
Solution 2 MusicMan24

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