二叉树基本操作

树model

package com.sly.uploadfile.algorithm;

/**
 * Created by fmgao on 2019/7/24.
 */
public class TreeNode01<T> {
    T value;
    TreeNode01<T> leftChild;
    TreeNode01<T> rightChild;

    TreeNode01() {
    }

    TreeNode01(T value) {
        this.value = value;
    }

    /**
     * 增加左子节点
     *
     * @param value
     */
    public void addLeft(T value) {
        TreeNode01<T> leftChild = new TreeNode01<T>();
        this.leftChild = leftChild;

    }

    /**
     * 增加右子节点
     *
     * @param value
     */
    public void addRight(T value) {
        TreeNode01<T> rightChild = new TreeNode01<>();
        this.rightChild = rightChild;
    }

    @Override
    public boolean equals(Object obj) {
        if (!(obj instanceof TreeNode01)) {
            return false;
        }
        return this.value.equals(((TreeNode01<?>) obj).value);
    }

    @Override
    public int hashCode() {
        return this.value.hashCode();
    }

    @Override
    public String toString() {
        return this.value == null ? "" : this.value.toString();
    }
}

树的基本操作

package com.sly.uploadfile.algorithm;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;

/**
 * Created by fmgao on 2019/7/24.
 */
public class TreeNodeTools {

    /**
     * 判断树种节点个数
     *
     * @param root
     * @param <T>
     * @return
     */
    public static <T> int getTreeNum(TreeNode01<T> root) {
        if (root == null) {
            return 0;
        }
        return getTreeNum(root.leftChild) + getTreeNum(root.rightChild) + 1;
    }

    /**
     * 判断树的深度
     *
     * @param root
     * @param <T>
     * @return
     */
    public static <T> int getTreeDepth(TreeNode01<T> root) {
        if (root == null) {
            return 0;
        }
        int leftDepth = getTreeDepth(root.leftChild) + 1;
        int rightDepth = getTreeDepth(root.rightChild) + 1;
        return Math.max(leftDepth, rightDepth);
    }

    /**
     * 前序遍历
     *
     * @param root
     * @param <T>
     */
    public static <T> void preOrderTravel(TreeNode01<T> root) {
        if (root == null) {
            return;
        }
        visitNode(root);
        preOrderTravel(root.leftChild);
        preOrderTravel(root.rightChild);

    }

    /**
     * 中序遍历
     *
     * @param root
     * @param <T>
     */
    public static <T> void midOrderTravel(TreeNode01<T> root) {
        if (root == null) {
            return;
        }
        midOrderTravel(root.leftChild);
        visitNode(root);
        midOrderTravel(root.rightChild);

    }

    /**
     * 后续遍历
     *
     * @param root
     * @param <T>
     */
    public static <T> void backOrderTravel(TreeNode01<T> root) {
        if (root == null) {
            return;
        }
        backOrderTravel(root.leftChild);
        backOrderTravel(root.rightChild);
        visitNode(root);

    }

    /**
     * 访问node节点
     *
     * @param node01
     * @param <T>
     */
    public static <T> void visitNode(TreeNode01<T> node01) {
        System.out.println(node01.value + "	");
    }

    /**
     * 分层遍历
     *
     * @param root
     * @param <T>
     */
    public static <T> void levelTravel(TreeNode01<T> root) {
        Queue<TreeNode01<T>> q = new LinkedList<TreeNode01<T>>();
        q.offer(root);
        while (!q.isEmpty()) {
            TreeNode01<T> tmp = q.poll();
            visitNode(tmp);
            if (tmp.leftChild != null) {
                q.offer(tmp.leftChild);
            }
            if (tmp.rightChild != null) {
                q.offer(tmp.rightChild);
            }
        }

    }

    /**
     * 求第K层节点个数
     *
     * @param root
     * @param k
     * @param <T>
     * @return
     */
    public static <T> int getNumForKLevel(TreeNode01<T> root, int k) {
        if (root == null || k < 1) {
            return 0;
        }
        if (k == 1) {
            return 1;
        }
        int leftNum = getNumForKLevel(root.leftChild, k - 1);
        int rightNum = getNumForKLevel(root.rightChild, k - 1);
        return leftNum + rightNum;
    }

    /**
     * 求二叉树种叶子节点的个数
     *
     * @param root
     * @param <T>
     * @return
     */
    public static <T> int getLeafNum(TreeNode01<T> root) {
        if (root == null) {
            return 0;
        }
        if (root.leftChild == null && root.rightChild == null) {
            return 1;
        }
        int leftNum = getLeafNum(root.leftChild);
        int rightNum = getLeafNum(root.rightChild);
        return leftNum + rightNum;
    }

    /**
     * 交换根节点的左右子树
     *
     * @param root
     * @param <T>
     * @return
     */
    public static <T> TreeNode01<T> exchange(TreeNode01<T> root) {
        if (root == null) {
            return null;
        }
        TreeNode01<T> left = exchange(root.leftChild);
        TreeNode01<T> right = exchange(root.rightChild);
        root.leftChild = right;
        root.rightChild = left;
        return root;
    }

    /**
     * 查看node是否是root的节点
     *
     * @param root
     * @param node
     * @param <T>
     * @return
     */
    public static <T> boolean nodeIsChild(TreeNode01<T> root, TreeNode01<T> node) {
        if (root == null || node == null) {
            return false;
        }
        if (root == node) {
            return true;
        }
        boolean isFind = nodeIsChild(root.leftChild, node);
        if (!isFind) {
            isFind = nodeIsChild(root.rightChild, node);
        }
        return isFind;
    }

    /**
     * 返回lNode 和 rNode 以root为根节点的公共父节点
     *
     * @param root
     * @param lNode
     * @param rNode
     * @param <T>
     * @return
     */
    public static <T> TreeNode01<T> findAllFatherNode(TreeNode01<T> root, TreeNode01<T> lNode, TreeNode01<T> rNode) {
        if (lNode == root || rNode == root) {
            return root;
        }
        if (root == null || lNode == null || rNode == null) {
            return null;
        }
        // 如果lNode是左子树的节点
        if (nodeIsChild(root.leftChild, lNode)) {
            if (nodeIsChild(root.rightChild, rNode)) {
                return root;
            } else {
                return findAllFatherNode(root.leftChild, lNode, rNode);
            }
        } else {
            if (nodeIsChild(root.leftChild, rNode)) {
                return root;
            } else {
                return findAllFatherNode(root.rightChild, lNode, rNode);
            }
        }
    }

    /**
     * 根据前序和中序构建二叉树
     *
     * @param pre
     * @param mid
     * @param <T>
     * @return
     */
    public static <T> TreeNode01<T> getTreeFromPreAndMid(List<T> pre, List<T> mid) {
        if (pre == null || mid == null || pre.size() == 0 || mid.size() == 0) {
            return null;
        }
        if (pre.size() == 1) {
            return new TreeNode01<T>(pre.get(0));
        }
        TreeNode01<T> root = new TreeNode01<T>(pre.get(0));
        // 找出根节点在中序中的位置
        int index = 0;
        while (!mid.get(index++).equals(pre.get(0))) {

        }

        // 构建左子树的前序
        List<T> preLeft = new ArrayList<T>(index);

        // 中子树的前序
        List<T> midLeft = new ArrayList<T>(index);
        for (int i = 1; i < index; i++) {
            preLeft.add(pre.get(i));
        }
        for (int i = 0; i < index - 1; i++) {
            midLeft.add(mid.get(i));
        }
        // 重建左子树
        root.leftChild = getTreeFromPreAndMid(preLeft, midLeft);
        // 右子树的前序
        List<T> preRight = new ArrayList<T>(pre.size() - index - 1);
        // 右子树的中序
        List<T> midRight = new ArrayList<T>(pre.size() - index - 1);
        for (int i = 0; i <= pre.size() - index - 1; i++) {
            preRight.add(pre.get(index + i));
        }

        for (int i = 0; i <= pre.size() - index - 1; i++) {
            midRight.add(mid.get(index + i));
        }
        // 重建→子树
        root.rightChild = getTreeFromPreAndMid(preRight, midRight);
        return root;

    }

    public static <T> boolean equals(TreeNode01<T> node1, TreeNode01<T> node2) {
        if (node1 == null && node2 == null) {
            return true;
        } else if (node1 == null || node2 == null) {
            return false;
        }
        boolean isEqual = node1.value.equals(node2.value);
        boolean isLeftEqual = equals(node1.leftChild, node2.leftChild);
        boolean isRightEqual = equals(node1.rightChild, node2.rightChild);
        return isEqual && isLeftEqual && isRightEqual;

    }

}