LintCode之632 二叉树最大节点

1
/   \
-5    2
/  \ /  \
0  3 -4 -5

public TreeNode maxNode(TreeNode root) {
// Write your code here
TreeNode result = null;
Stack<TreeNode> stack = new Stack<TreeNode>();
while(root != null || !stack.empty()){
while (root != null) {
if (result==null||result.val < root.val) {
result = root;
}
stack.push(root);
root = root.left;
}
if(!stack.empty()){
root = stack.lastElement();
stack.pop();
if (result==null||result.val < root.val) {
result = root;
}
root = root.right;
}
}
return result;
}