ChildrenSumProperty

/*************************************************************

    Following is the Binary Tree node structure

    class BinaryTreeNode < Integer > {
        int data;
        BinaryTreeNode < Integer > left;
        BinaryTreeNode < Integer > right;

    public BinaryTreeNode(int data) {
            this.data = data;
        }
    }

*************************************************************/

public class Solution {
    public static void changeTree(BinaryTreeNode < Integer > root) {
        if(root==null)
            return;
        
        int child = 0;
        if(root.left!=null)
            child += root.left.data;
        
        if(root.right!=null)
            child += root.right.data;
        
        if(child>=root.data)
            root.data = child;
        else{
            if(root.left!=null)
                root.left.data = root.data;
            else if(root.right!=null)
                root.right.data = root.data;
        }
        
        changeTree(root.left);
        changeTree(root.right);
        
        int tot = 0;
        if(root.left!=null)
            tot += root.left.data;
        if(root.right!=null)
            tot += root.right.data;
        if(root.left!=null || root.right!=null)
            root.data = tot;
            
    }
}