二叉树遍历算法-优快云博客

本文链接：https://blog.youkuaiyun.com/wangche320/article/details/43879399

本文介绍了二叉树的三种遍历方式：前序遍历、中序遍历及后序遍历，并提供了详细的实现代码。每种遍历方法都使用了栈来辅助实现，通过迭代的方式而非递归，使得代码更加高效且易于理解。

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    public static void preOrder(Node root){
        //check
        Stack stack = new Stack();  
        Node p = root;  
        while(p != null){
            stack.push(p);
            System.out.print(p.value + " ");
            if(p.left != null){   
                p = p.left;  
                continue;
            }
            while(true){
                Node node = (Node)stack.pop();
                if(node == null) {
                    return;
                }
                if(node.right != null){
                    p = node.right;
                    break;
                }
            }
        }
    }

public static void inOrder(Node root){  
        //check
        Stack stack = new Stack();  
        Node p = root;  
        while(p != null){  
            stack.push(p);  
            if(p.left != null){   
                p = p.left;  
                continue;
            }  
            while(true){
                Node node = (Node)stack.pop();
                if(node == null) {
                    return;
                }
                System.out.print(node.value + " ");
                if(node.right != null){
                    p = node.right;
                    break;
                }
            }
        }  
    }

    public static void postOrder(Node root){
        //check
        Stack stack = new Stack();
        Node p = root;
        while(p != null){
            stack.push(p);
            if(p.left != null){
                p = p.left;
                continue;
            }
            Node last = null;
            while(true){
                Node node = (Node)stack.peek();
                if(node == null){//根节点
                    return;
                }
                //要记下上次的点，避免处理完右子节点，接着处理父节点时陷入死循环
                if((node.right == null) || (node.right == last)){
                    last = (Node)stack.pop();
                    System.out.print(node.value + " ");
                }else{
                    p = node.right;
                    break;
                }
            }
        }
    }

非递归遍历二叉树