如图:
public class TreeNode0 {
public int val;
public TreeNode0 left;
public TreeNode0 right;
public TreeNode0() {}
public TreeNode0(int val) { this.val = val; }
TreeNode0(int val, TreeNode0 left, TreeNode0 right) {
this.val = val;
this.left = left;
this.right = right;
}
}