二叉树的非递归遍历

Posted 2020-10-05 blythe

 // 先序遍历非递归     
    public static void preOrder2(BinTree t) {    
        Stack<BinTree> s = new Stack<BinTree>();    
        while (t != null || !s.empty()) {    
            while (t != null) {    
                System.out.print(t.date);    
                s.push(t);    
                t = t.lchild;    
            }    
            if (!s.empty()) {    
                t = s.pop();    
                t = t.rchild;    
            }    
        }    
    }    
    
    // 中序遍历非递归     
    public static void InOrder2(BinTree t) {    
        Stack<BinTree> s = new Stack<BinTree>();    
        while (t != null || !s.empty()) {    
            while (t != null) {    
                s.push(t);    
                t = t.lchild;    
            }    
            if (!s.empty()) {    
                t = s.pop();    
                System.out.print(t.date);    
                t = t.rchild;    
            }    
        }    
    }    
    
    // 后序遍历非递归     
    public static void PostOrder2(BinTree t) {    
        Stack<BinTree> s = new Stack<BinTree>();    
        Stack<Integer> s2 = new Stack<Integer>();    
        Integer i = new Integer(1);    
        while (t != null || !s.empty()) {    
            while (t != null) {    
                s.push(t);    
                s2.push(new Integer(0));    
                t = t.lchild;    
            }    
            while (!s.empty() && s2.peek().equals(i)) {    
                s2.pop();    
                System.out.print(s.pop().date);    
            }    
    
            if (!s.empty()) {    
                s2.pop();    
                s2.push(new Integer(1));    
                t = s.peek();    
                t = t.rchild;    
            }    
        }    
    }    
    

 

 public void thePostOrderTraversal_Stack(Node root) {   //后序遍历  
        Stack<Node> stack = new Stack<Node>();  
        Stack<Node> output = new Stack<Node>();//构造一个中间栈来存储逆后序遍历的结果  
        Node node = root;  
        while (node != null || stack.size() > 0) {  
            if (node != null) {  
                output.push(node);  
                stack.push(node);                 
                node = node.getRightNode();  
            } else {  
                node = stack.pop();               
                node = node.getLeftNode();
            }  
        }  
        System.out.println(output.size());
        while (output.size() > 0) {
            
            printNode(output.pop());  
        }  
    }