2019-12-23 前序遍历二叉树

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public class JsonArrayTest {
   

    public static void main(String[] args) {

        TreeNode[] node = new TreeNode[10];//以数组形式生成一棵完全二叉树
        for(int i = 0; i < 10; i++)
        {
            node[i] = new TreeNode(i);
        }
        for(int i = 0; i < 10; i++)
        {
            if(i*2+1 < 10)
                node[i].left = node[i*2+1];
            if(i*2+2 < 10)
                node[i].right = node[i*2+2];
        }

        preOrderRe(node[0]);

    }


    public static void preOrderRe(TreeNode biTree)
    {//递归实现
        System.out.println(biTree.value);
        TreeNode leftTree = biTree.left;
        if(leftTree != null)
        {
            preOrderRe(leftTree);
        }
        TreeNode rightTree = biTree.right;
        if(rightTree != null)
        {
            preOrderRe(rightTree);
        }
    }

    public static void preOrder(TreeNode biTree)
    {//非递归实现
        Stack stack = new Stack();
        while(biTree != null || !stack.isEmpty())
        {
            while(biTree != null)
            {
                System.out.println(biTree.value);
                stack.push(biTree);
                biTree = biTree.left;
            }
            if(!stack.isEmpty())
            {
                biTree = stack.pop();
                biTree = biTree.right;
            }
        }
    }


    static class TreeNode//节点结构
    {
        int value;
        TreeNode left;
        TreeNode right;

        TreeNode(int value) {
            this.value = value;
        }
    }

    }