Recursive method not trans versing all of a tree node

Question

I have a findNode method that finds a target string in a treenode. The issue I am having is that my recursive method only seems to go down one branch of the tree and not cover the hole tree like I thought it should. If you require anymore code please ask.

public GeneralTreeNode findNode(String targetName) {
  // name is the current name of the node
  if(targetName.equals(this.name)) return this;
  // children is a HashSet of all the nodes children
  for(GeneralTreeNode child : children) return child.findNode(targetName);

  // no node containing the string could be found
  return null; 
}

Thanks for all responses!

Dan_ENZ
– Dan_ENZ

2014-09-25 08:20:22 +00:00
Commented Sep 25, 2014 at 8:20 — Dan_ENZ
– Dan_ENZ, Commented Sep 25, 2014 at 8:20

Evan Knowles · Accepted Answer · 2014-09-25 08:13:45Z

1

You're returning in your loop, hence why it stops. Instead of always returning, only return if you find something.

for(GeneralTreeNode child : children) {
   GeneralTreeNode result = child.findNode(targetName);
   if (result != null) {
        return result;
   }

}

answered Sep 25, 2014 at 8:13

Evan Knowles

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1 Comment

Dan_ENZ Over a year ago

Thanks! knew I wasn't far off. Makes a lot more sense.

przemek hertel · Accepted Answer · 2014-09-25 08:13:11Z

0

Change to such chode:

public GeneralTreeNode findNode(String targetName) {

  // name is the current name of the node
  if(targetName.equals(this.name)) return this;

  // children is a HashSet of all the nodes children
  for(GeneralTreeNode child : children) { 
     GeneralTreeNode result = child.findNode(targetName);
     if (result != null) return result;
  }

  // no node containing the string could be found
  return null; 
}

This should work as you want...

answered Sep 25, 2014 at 8:13

przemek hertel

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2 Comments

Evan Knowles Over a year ago

This will not compile, you have the return in the result assignment.

przemek hertel Over a year ago

True, this is typo mistake, i have edited. thanks @Evan

Seelenvirtuose · Accepted Answer · 2014-09-25 08:15:18Z

0

In this line

for(GeneralTreeNode child : children) return child.findNode(targetName);

you directly return the result from the first child. So each subsequent child will never be consulted. As this first child also returns the result from its first child, you observe that your method only considers one branch.

The solution is to analyze the result of each child:

for(GeneralTreeNode child : children) {
    GeneralTreeNode result = child.findNode(targetName);
    if (result != null) return result;
}

Now it only returns the result, if the node was really found. If not, the loop continues.

answered Sep 25, 2014 at 8:15

Seelenvirtuose

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