X327: Binary Tree Has Path Sum Exercise (Modified)

We define a "root-to-leaf path" to be any sequence of nodes in a tree starting with the root node and proceeding downward to a leaf. The "root-to-leaf path sum" for that path is the sum of the values for all the nodes (including the root) along that path. Define an empty tree to contain no root-to-leaf paths (and so its sum is zero). Define a tree with one node to have a root-to-leaf path consisting of just the root (and so its sum is the value of the root). Given a binary tree and a value sum, return true if the tree has some root-to-leaf path such that adding up all the values along the path equals sum. Return false if no such path exists.
Here are methods that you can use on the BinNode objects:
   interface BinNode {
      public int value();
      public void setValue(int v);
      public BinNode left();
      public BinNode right();
      public boolean isLeaf();


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