write a program to print only the peripheral nodes of binary tree

Question

Saket · Accepted Answer

Java code:

    public void peripheralNodes(){
        peripheralNodes(root);
    }
    
    private void peripheralNodes(Node node){
    System.out.print(node.data+" ");
        sideNodes(node.left,"left");
        leafNodes(node);
        sideNodes(node.right,"right");
        
    }
    
    private void sideNodes(Node node, String side){
        if(node == null)
        return;
        if(node.left == null & node.right == null)
        return;
        if(node != null && side.equalsIgnoreCase("left"))
        System.out.print(node.data+" ");
        if(side.equalsIgnoreCase("left"))
        sideNodes(node.left,side);
        else
        sideNodes(node.right,side);
        if(node != null && side.equalsIgnoreCase("right"))
        System.out.print(node.data+" ");
      }

The above algo takes O(n)+O(No. of left & right  nodes)
Is there any other effective way ?

Aditya Rawat · Answer

It's quite simple if you think about it. 
1.Print all the left peripherals. Recurse left until you reach the end printing everything.
2.Repeat the same for the right periphery. 
3. Print all the leaf nodes except the left most and the right most.

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