CODEWITHSUNDEEP
javabinary-tree
Yeyez
Yeyez

Reputation: 17

why the return statement is not executing?

I'm trying to implement a find method in a binary tree. The problem appears when the method needs to return a value but it seems like its not executing that statement even when have other lines in the same semicolon that executes.

public String find(Node currentNode, String value)
{
    if(isEmpty())
    {
        return null;
    }
    else
    {
        if(currentNode.getData().compareToIgnoreCase(value) == 0)
        {
            System.out.println("current -> "+currentNode.getData()); //showing
            return currentNode.getData(); //not executing
        }

        if(value.compareToIgnoreCase(currentNode.getData()) < 0)
        {
            find(currentNode.getLeft(), value);
        }
        else if(value.compareToIgnoreCase(currentNode.getData()) > 0)
        {
            find(currentNode.getRight(), value);
        }
    }

    return null; //always executing
}

i expect "a" but returns null.

Upvotes: 1

Views: 426

Answers (2)

Schidu Luca
Schidu Luca

Reputation: 3947

You have to use the data that returns your recursive call, right now you are ignoring it. Also you always return null no matter what, here's a fixed version of the program:

public String find(TreeNode currentNode, String value) {
    if (currentNode == null) {
        return null;
    }

    if(currentNode.getData().compareToIgnoreCase(value) == 0) {
        return currentNode.getData(); //not executing
    }

    if (currentNode.getData().compareToIgnoreCase(value) > 0) {
        return find(currentNode.getLeft(), value);
    } else {
        return find(currentNode.getRight(), value);
    }
}

Upvotes: 1

rgettman
rgettman

Reputation: 178293

When you execute the line

find(currentNode.getLeft(), value);

Your statement return currentNode.getData(); is executing, but you are ignoring what your recursive call has returned. (Similar for the getRight() statement.) Then the if/else statement completes and the return null at the bottom executes. That is why you are always getting null.

Return whatever the recursive call returns, so that the returned value propagates back to the original call properly, e.g.:

return find(currentNode.getLeft(), value);

Upvotes: 6

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