Thread: Help with recursion

I was wondering if someone could show me how to turn my code into a recursive method to build my binary tree. I am new to recursion and it doesn't make a whole lot of sense to me.

//===============================================================================================
	// BinaryTree constructor - Takes the string and turns it into an array based on parenthesis.
	// Loops through using a stack and adds children that fall within parent parenthesis
	//===============================================================================================
	public BinaryTree(String inputString) throws InvalidTreeSyntax {
 
		Stack<Node> nodeStack = new Stack<>();
 
		String[] inputArray = inputString.substring(1, inputString.length()-1) // remove first & last parenthesis
				//and split the String into a arr of strings, retain the parenthesis
				.split("(?<=\\()|(?=\\()|(?<=\\))|(?=\\))");
 
		parentNode = new Node(inputArray[0]); //setting the new first character to the root
 
		//starts essentially on the third character of the string
		for (int i = 1; i < inputArray.length - 1; i++) {
 
			//means there is another child. Child becomes parent if one exists
			if (inputArray[i].equals("(")) { 
				nodeStack.push(parentNode);
 
				if (childNode != null) { 
					parentNode = childNode; 
				}
				//assign the current parent as the child of one on stack
			}
			else if(inputArray[i].equals(")")) {
				try { 
					childNode = parentNode; 
					parentNode = nodeStack.pop();
				}
				catch (EmptyStackException e) { 
					throw new InvalidTreeSyntax("Incorrect parenthesis!"); 
				}
				//if it gets here, it is a value to be assigned as child to parent.
			}
			else { 
				childNode = new Node(inputArray[i]);
				if (parentNode != null) { 
					parentNode.addChild(childNode); 
				}//addChild with throw InvalidTreeSyntax
			}
		}//for every node, will have 2 parenthesis
		if (this.nodesCheck(parentNode) * 3 != inputString.length()) throw new InvalidTreeSyntax("Incorrect Syntax");
	}

great video on how to do recursive programming (dynamic programming) the right way

https://youtu.be/oBt53YbR9Kk

Originally Posted by AngleWyrm

great video on how to do recursive programming (dynamic programming) the right way

Very useful for me!