Binary Search Tree DFS Template

Two methods:

1. Traverse

2. Divide & Conquer

// Traverse: usually do not have return value
public class Solution {
    public void traverse(TreeNode root) {
        if (root == null)
            return;
        traverse(root.left);
        traverse(root.right);
    }
}

// Divide & Conquer: usually have return value
public class Solution {
    public ResultType traversal(TreeNode root) {
        if (root == null) {
            // do something and return
        }

        // Divide
        ResultType left = traversal(root.left);
        ResultType right = traversal(root.right);

        // Conquer
        ResultType merge = Merge from left to right.
        return result;
    }
}