二叉树的创建及前中后层遍历

package com.data.tree;

/**
 * ClassName TreeTest Description TODO
 * @author Payphone
 * @date 2018年12月24日 下午1:44:07
 * @version V1.0
 */
public class TreeTest {
    public static int maxsize = 100;

    public static void main(String[] args) {
        String[] arr = { "A", "B", "C", "D", "E", "#", "#", "#", "#", "#", "#" };

        TreeTest ts = new TreeTest();
        BiTree tree = ts.createTree(new BiTree(), arr);
        ts.levelOrder(tree);
        System.out.println(tree.toString());
    }

    
　　

package com.data.tree;

public class BiTree {
    String data;//数据域
    BiTree left,right;//下一个结点
    int leval;//层数
}

 

　　/**
     * @Title createTree
     * @Description 层序建二叉树
     * @param bt
     * @param node
     * @return BiTree
     */
    BiTree createTree(BiTree bt, String[] node) {
        int rear = -1, front = -1;
        BiTree[] queue = new BiTree[maxsize];// 定义队列
        int flag = 0;// 数组下标
        bt = new BiTree();
        bt.data = node[flag++];// 给根节点赋值
        queue[++rear] = bt;// 根节点入队
        // 数组未读取完毕且队列非空时
        while (flag < node.length && !(rear == front)) {
            BiTree b = queue[++front];
            // 给出队的节点 创建左子树
            if (node[flag] == "#") {
                b.left = null;
                flag++;
            } else {
                b.left = new BiTree();
                b.left.data = node[flag++];
                // 左子树非空则入队
                queue[++rear] = b.left;
            } // end if
                // 给出队的节点创建右子树
            if (node[flag] == "#") {
                b.right = null;
                flag++;
            } else {
                b.right = new BiTree();
                b.right.data = node[flag++];
                // 右子树非空入队
                queue[++rear] = b.right;
            } // end if
        }
        return bt;
    }

    /**
     * @Title levelOrder
     * @Description 
     *         二叉树的层序遍历
     *         节点出队打印 左右子树入队
     * @param tree
     * @return void
     */
    public void levelOrder(BiTree tree) {
        int rear = -1,front = -1;
        BiTree[] queue = new BiTree[maxsize];
        queue[++rear] = tree;
        while(rear!=front) {
            BiTree bt = queue[++front];
            System.out.println(bt.data);
            if(bt.left!=null) {
                queue[++rear] = bt.left;
            }
            if(bt.right!=null) {
                queue[++rear] = bt.right;
            }
        }
    }
    
    
    //先序遍历
    public void PreNode(BiTree tree) {
        if (tree != null) {
            System.out.println(tree.data);
            PreNode(tree.left);
            PreNode(tree.right);
        }
    }

    /*
     * 先序遍历思想： 先把左子树一直入栈 左子树到头了在从栈中弹出元素 看弹出的元素是否有右节点 有就继续按先序来
     */
    public void PreNodeUn(BiTree tree) {
        int top = -1;
        BiTree[] stack = new BiTree[maxsize];
        while (top != -1 || tree != null) {
            if (tree != null) {
                System.out.println(tree.data);
                stack[++top] = tree;
                tree = tree.left;
            } else {
                tree = stack[top--];
                tree = tree.right;
            }
        }
    }

    public void PreNodeUn1(BiTree tree) {
        int top = -1;
        BiTree[] stack = new BiTree[maxsize];
        while (top != -1 || tree != null) {
            while (tree != null) {
                System.out.println(tree.data);
                stack[++top] = tree;
                tree = tree.left;
            }
            if (tree == null) {
                tree = stack[top--];
                tree = tree.right;
            }
        }
    }

    // 中序遍历
    public void InOrder(BiTree tree) {
        InOrder(tree.left);
        System.out.println(tree.data);
        InOrder(tree.right);
    }

    // 中序遍历
    public void InOrderUn(BiTree tree) {
        int top = -1;
        BiTree[] stack = new BiTree[maxsize];// 定义栈
        while (top != -1 || tree != null) {
            while (tree != null) {
                stack[++top] = tree;
                tree = tree.left;
            }
            if (tree == null) {
                tree = stack[top--];
                System.out.println(tree.data);
                tree = tree.right;
            }
        }
    }

    // 后序遍历
    void PostOrder(BiTree tree) {
        PostOrder(tree.left);
        PostOrder(tree.right);
        System.out.println(tree.data);
    }

    // 后序非递归
    void PostOrderUn(BiTree tree) {
        BiTree flag = null;
        int top = -1;
        BiTree[] stack = new BiTree[maxsize];
        while (top != -1 || tree != null) {
            while (tree != null) {// 左子树一直入栈
                stack[++top] = tree;
                tree = tree.left;
            }
            // 左子树访问到头了
            if (tree == null) {
                tree = stack[top];// 获取栈顶 看其是否有右子树
                if (tree.right != null && tree.right != flag) {// 有右子树且未被访问过
                    tree = tree.right;// 以右子树为根继续进行其左子树的入栈操作
                } else {// 左右都已经访问完毕了。[第一次访问的一定是叶子节点，它没有左右子树]
                    System.out.println(tree.data);
                    top--;// 元素出栈
                    flag = tree;// flag表示已经访问了。
                    tree = null;// 让下一个元素出栈
                }
            }
        }
    }
}