How to print elements from a binary tree ignoring all the repeating ones?

问题

 public void printTree(node root)
    {
        if(root != null)
        {
            printTree(root.left);
            System.out.print(root.word + " " + root.line+" ");
            String tempStr=root.word; int tempLn=root.line; //don't know how to use it
            printTree(root.right);
        }
    }

Assume that the tree is already sorted in a lexicographic order.

For example, the file is like this:

aaa 
zzz
the the the the 

and the output should be like this:

aaa line: 1
the line: 3 3 3 3
zzz line: 2

My code now displays the same words for many times. I don't know how to organize this chunk of code.

回答1:

The problem is that you are instantly outputting information as you find it. Instead, you need to store the data you come across in a continual fashion.

You will probably want to use a HashMap<String, List<Integer>> data structure to hold this information.

回答2:

You can use a HashMap to store pairs of <String, List>, where String will be your key and List will be a list of positions, where such key was found. If you need to check, if a key is already in the map, you do

map.contains(key);

and if there is one, you can update the appropriate list by doing

map.get(key).add(page);

来源：https://stackoverflow.com/questions/21841283/how-to-print-elements-from-a-binary-tree-ignoring-all-the-repeating-ones