问题
Returning a single value through recursion works just fine. But what if I want to return a list of values that recursion goes through each call. Here's my code.
public void inOrder(Node focusNode) {
/* ArrayList<Integer> tempList = new ArrayList<Integer>(); */
if ( focusNode != null) {
inOrder(focusNode.getLeftNode());
System.out.println(focusNode);
/* tempList.add(focusNode.getElement()); */
inOrder(focusNode.getRightNode());
}
/* int[] elems = new int[tempList.toArray().length];
int i = 0;
for ( Object o : tempList.toArray())
elems[i++] = Integer.parseInt(o.toString()); */
//return tempList;
}
printing values while traversing through gives the expected output. But storing those values is not working. It only returns with a single value in a list. Can someone help me with this?
回答1:
Why don't you just pass in a reference to an array list along with your starting node? After your inOrder method runs, you'll have an ordered series of values that you can use as you please.
// method signature changed
public void inOrder(Node focusNode, ArrayList vals) {
/* ArrayList<Integer> tempList = new ArrayList<Integer>(); */
if ( focusNode != null) {
// args changed here
inOrder(focusNode.getLeftNode(), vals);
// adding node to array list rather than dumping to console
vals.add(focusNode);
/* tempList.add(focusNode.getElement()); */
inOrder(focusNode.getRightNode());
}
来源：https://stackoverflow.com/questions/38531849/how-to-return-a-list-of-values-through-recursion-in-java