非递归二叉树操作.md

使用单栈进行二叉树非递归操作。
具体的Java版本代码为：

protected static void nonIterativePreorder(Node p) {    
    Stack<Node> stack = new Stack<Node>();    
    Node node = p;    
    while (node != null || stack.size() > 0) {    
        while (node != null) {
            visit(node);    
            stack.push(node);    
            node = node.getLeft();    
        }    
        if (stack.size() > 0) { 
            node = stack.pop();    
            node = node.getRight();    
        }    
    }    
} 

 protected static void noniterativeInorder(Node p) {    
    Stack<Node> stack = new Stack<Node>();    
    Node node = p;    
    while (node != null || stack.size() > 0) {    
        while (node != null) {    
            stack.push(node);    
            node = node.getLeft();    
        }    
        if (stack.size() > 0) {    
            node = stack.pop();    
            visit(node);
            node = node.getRight();    
        }    
    }    
}

 protected static void noniterativePostorder(Node p) {    
    Stack<Node> stack = new Stack<Node>();    
    Node node = p, prev = p;    
    while (node != null || stack.size() > 0) {    
        while (node != null) {    
            stack.push(node);    
            node = node.getLeft();    
        }    
        if (stack.size() > 0) {    
            Node temp = stack.peek().getRight();    
            if (temp == null || temp == prev) {    
                node = stack.pop();    
                visit(node);    
                prev = node;    
                node = null;    
            } else {    
                node = temp;    
            }    
        }
    }    
}