中序遍历

class Node {
   int data;
    Node left, right;

   Node(int item) {
      data = item;
     left = right = null;
    }
   }

   public class A031 {
   Node root;
   int diameter = 0;
    public int diameterOfBinaryTree(Node root) {  
          getDepth(root);  
            return diameter;  
       }
        // 此函数是返回树的最大深度  
        private int getDepth(Node root) {  
          if (root == null)  
              return 0;  
          int l = getDepth(root.left);  
           int r = getDepth(root.right);  
          diameter = Math.max(diameter, l + r);  
          return Math.max(l, r) + 1;  
     } 
    public static void main(String args[]) {
      
     A031 tree = new A031();

     tree.root = new Node(1);
     tree.root.left = new Node(2);
    tree.root.right = new Node(3);
   tree.root.left.left = new Node(5);
   tree.root.left.right = new Node(6);
      tree.root.left.left.left = new Node(7);
      tree.root.left.left.right = new Node(8);
     System.out.println(tree.diameterOfBinaryTree(tree.root)+1);
     }
}