Java打印树形结构

序言

最近在学习算法相关的东西，有一些树形结构的数据需要打印出来开对不对，比如二分搜索树，于是我就写了一个工具类。希望能帮到大家

效果

源码

BST(二分搜索树)

package com.zgh.algorithm.search;import java.util.HashMap;import java.util.Iterator;import java.util.Map;import com.zgh.algorithm.search.TreePrintUtil.TreeNode;/** * 二分搜索树 *  * @author zhuguohui * */public class BST<K extends Comparable<K>, V> {    private int count;    private Node<K, V> root;    private int maxLevel;    public int size() {        return count;    }    public boolean isEmpty() {        return count == 0;    }    public void insert(K k, V v) {        Node<K, V> node = new Node<>(k, v);        if (insertToNode(root, node, 0)) {            // 如果是插入则将count+1            count++;        }    }    public Node getRoot() {        return root;    }    /**     *      * @param parint     * @param node     * @return 如果新增返回true，如果只是更新返回false     */    private boolean insertToNode(Node<K, V> parent, Node<K, V> node, int level) {        if (root == null) {            root = node;            maxLevel = 1;            return true;        }        if (parent.k.compareTo(node.k) == 0) {            // key相同则更新            parent.v = node.v;            return false;        } else if (parent.k.compareTo(node.k) < 0) {            // 如果node比parent大，则插入到右子树            if (parent.right == null) {                parent.right = node;                if (level + 1 > maxLevel) {                    maxLevel = level + 1;                }                return true;            }            return insertToNode(parent.right, node, level + 1);        } else {            // 如果node比parent小，则插入左字数            if (parent.left == null) {                parent.left = node;                if (level + 1 > maxLevel) {                    maxLevel = level + 1;                }                return true;            }            return insertToNode(parent.left, node, level + 1);        }    }    private static class Node<K extends Comparable<K>, V> implements TreeNode {        K k;        V v;        Node left, right;        public Node(K k, V v) {            this.k = k;            this.v = v;        }        @Override        public String toString() {            return "[" + k + "]";        }        @Override        public String getPrintInfo() {            return toString();        }        @Override        public TreeNode getLeftChild() {            // TODO Auto-generated method stub            return left;        }        @Override        public TreeNode getRightChild() {            // TODO Auto-generated method stub            return right;        }    }}

TreePrintUtil(打印树形结构工具类)

package com.zgh.algorithm.search;import java.util.HashMap;import java.util.Iterator;import java.util.Map;public class TreePrintUtil {    public static void pirnt(TreeNode root) {        // 找到左边的最大偏移量        int maxLeftOffset = findMaxOffset(root, 0, true);        int maxRightOffset = findMaxOffset(root, 0, false);        int offset = Math.max(maxLeftOffset, maxRightOffset);        // 计算最大偏移量        Map<Integer, PrintLine> lineMap = new HashMap();        calculateLines(root, offset, lineMap, 0, true);        Iterator<Integer> lineNumbers = lineMap.keySet().iterator();        int maxLine = 0;        while (lineNumbers.hasNext()) {            int lineNumber = lineNumbers.next();            if (lineNumber > maxLine) {                maxLine = lineNumber;            }        }        for (int i = 0; i <= maxLine; i++) {            PrintLine line = lineMap.get(i);            if (line != null) {                System.out.println(line.getLineString());            }        }    }    private static void calculateLines(TreeNode parent, int offset, Map<Integer, PrintLine> lineMap, int level,            boolean right) {        if (parent == null) {            return;        }        int nameoffset = parent.toString().length() / 2;        PrintLine line = lineMap.get(level);        if (line == null) {            line = new PrintLine();            lineMap.put(level, line);        }        line.putString(right ? offset : (offset - nameoffset), parent.toString());        // 判断有没有下一级        if (parent.getLeftChild() == null && parent.getRightChild() == null) {            return;        }        // 如果有，添加分割线即/\        PrintLine separateLine = lineMap.get(level + 1);        if (separateLine == null) {            separateLine = new PrintLine();            lineMap.put(level + 1, separateLine);        }        if (parent.getLeftChild() != null) {            separateLine.putString(offset - 1, "/");            calculateLines(parent.getLeftChild(), offset - nameoffset - 1, lineMap, level + 2, false);        }        if (parent.getRightChild() != null) {            separateLine.putString(offset + nameoffset + 1, "\\");            calculateLines(parent.getRightChild(), offset + nameoffset + 1, lineMap, level + 2, true);        }    }    /**     * 需要打印的某一行     *      * @author zhuguohui     *     */    private static class PrintLine {        /**         * 记录了offset和String的map         */        Map<Integer, String> printItemsMap = new HashMap<>();        int maxOffset = 0;        public void putString(int offset, String info) {            printItemsMap.put(offset, info);            if (offset > maxOffset) {                maxOffset = offset;            }        }        public String getLineString() {            StringBuffer buffer = new StringBuffer();            for (int i = 0; i <= maxOffset; i++) {                String info = printItemsMap.get(i);                if (info == null) {                    buffer.append(" ");                } else {                    buffer.append(info);                    i += info.length();                }            }            return buffer.toString();        }    }    private static int findMaxOffset(TreeNode parent, int offset, boolean findLeft) {        if (parent != null) {            offset += parent.toString().length();        }        if (findLeft && parent.getLeftChild() != null) {            offset += 1;            return findMaxOffset(parent.getLeftChild(), offset, findLeft);        }        if (!findLeft && parent.getRightChild() != null) {            return findMaxOffset(parent.getRightChild(), offset, findLeft);        }        return offset;    }    public interface TreeNode {        String getPrintInfo();        TreeNode getLeftChild();        TreeNode getRightChild();    }}

使用

要实现打印需要有两步，

第一步

让你的Node类实现TreePrintUtil中的TreeNode接口

    public interface TreeNode {        /**         * 需要打印的信息         * @return         */        String getPrintInfo();        TreeNode getLeftChild();        TreeNode getRightChild();    }

实现如下

private static class Node<K extends Comparable<K>, V> implements TreeNode {        K k;        V v;        Node left, right;        public Node(K k, V v) {            this.k = k;            this.v = v;        }        @Override        public String toString() {            return "[" + k + "]";        }        @Override        public String getPrintInfo() {            return toString();        }        @Override        public TreeNode getLeftChild() {            // TODO Auto-generated method stub            return left;        }        @Override        public TreeNode getRightChild() {            // TODO Auto-generated method stub            return right;        }    }

第二步

返回根元素

    public Node getRoot() {        return root;    }

使用如下

package com.zgh.algorithm.search;public class Demo2 {    public static void main(String[] args) {        BST<Integer, String> bst = new BST<>();        bst.insert(10, "a");        bst.insert(12, "b");        bst.insert(3, "d");        bst.insert(9, "cdd");        bst.insert(33, "cff");        bst.insert(38, "ceee");        bst.insert(1, "aaaa");        bst.insert(0, "dddd");        bst.insert(99, "dddd");        bst.insert(100, "dddd");        bst.insert(7, "dddd");        bst.insert(1, "dddd");        //从根开始打印        TreePrintUtil.pirnt(bst.getRoot());    }}