二叉树的简单学习Java版

构建一个二叉树

//二叉树
class BinaryTree {
    private HeroNode root;

    public void setRoot(HeroNode root) {
        this.root = root;
    }

    public void delNode(int no){
        if (root != null) {
            if (root.getNo() == no) {
                root = null;
            }else {
                root.delNode(no);
            }
        }else {
            System.out.println("空树无法删除");
        }
    }

    public void preOrder() {
        if (this.root != null) {
            this.root.preOrder();
        } else {
            System.out.println("二叉树为空，无法遍历");
        }
    }

    public void infixOrder() {
        if (this.root != null) {
            this.root.infixOrder();
        } else {
            System.out.println("二叉树为空，无法遍历");
        }
    }

    public void postOrder() {
        if (this.root != null) {
            this.root.postOrder();
        } else {
            System.out.println("二叉树为空，无法遍历");
        }
    }

    //前序遍历查找
    public HeroNode preOrderSearch(int no) {
        if (root != null) {
            return root.preOrderSearch(no);
        } else {
            return null;
        }
    }

    //前序遍历查找
    public HeroNode infixOrderSearch(int no) {
        if (root != null) {
            return root.infixOrderSearch(no);
        } else {
            return null;
        }
    }

    //前序遍历查找
    public HeroNode postOrderSearch(int no) {
        if (root != null) {
            return root.postOrderSearch(no);
        } else {
            return null;
        }
    }
}

class HeroNode {
    private int no;
    private String name;
    private HeroNode left;
    private HeroNode right;

    public HeroNode(int no, String name) {
        this.no = no;
        this.name = name;
    }

    public int getNo() {
        return no;
    }

    public void setNo(int no) {
        this.no = no;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public HeroNode getLeft() {
        return left;
    }

    public void setLeft(HeroNode left) {
        this.left = left;
    }

    public HeroNode getRight() {
        return right;
    }

    public void setRight(HeroNode right) {
        this.right = right;
    }

    @Override
    public String toString() {
        return "HeroNode{" +
                "no=" + no +
                ", name='" + name + '\'' +
                '}';
    }

    //递归删除节点，如果是叶子节点就删除该节点，如果是非叶子节点就删除该子树
    public void delNode(int no) {
        //思路
        /**
         *        因为二叉树是单向的，所以我们判断当前节点的子节点是否是需要删除的节点，
         * 如果当前节点的左子节点不为空，并且左子节点就是要删除节点，就将左边置空
         * 如果右子节点不为空，并且右子节点就是，将右子节点置空
         * 如果上面都不是就向左子树递归，
         * 右子树递归
         */
        if (this.left != null && this.left.no == no) {
            this.left = null;
            return;
        }
        if (this.right != null && this.right.no == no) {
            this.right = null;
            return;
        }
        if (this.left != null) {
            this.left.delNode(no);
        }
        if (this.right != null) {
            this.right.delNode(no);
        }
    }


    //节点前序遍历
    public void preOrder() {
        System.out.println(this);
        if (this.left != null) {
            this.left.preOrder();
        }
        if (this.right != null) {
            this.right.preOrder();
        }
    }

    //中序遍历
    public void infixOrder() {
        //递归向左子树中序遍历
        if (this.left != null) {
            this.left.infixOrder();
        }
        System.out.println(this);
        if (this.right != null) {
            this.right.infixOrder();
        }
    }

    //后序遍历
    public void postOrder() {
        if (this.left != null) {
            this.left.postOrder();
        }
        if (this.right != null) {
            this.right.postOrder();
        }
        System.out.println(this);
    }

    //前序遍历查找
    public HeroNode preOrderSearch(int no) {
        //比较当前节点是不是
        if (this.no == no) {
            return this;
        }
        HeroNode result = null;
        if (this.left != null) {
            result = this.left.preOrderSearch(no);
        }
        if (result != null) {
            return result;
        }
        if (this.right != null) {
            result = this.right.preOrderSearch(no);
        }
        return result;
    }

    //中序遍历查找
    public HeroNode infixOrderSearch(int no) {
        HeroNode result = null;
        if (this.left != null) {
            result = this.left.infixOrderSearch(no);
        }
        if (result != null) {
            return result;
        }
        if (this.no == no) {
            return this;
        }
        if (this.right != null) {
            result = this.right.infixOrderSearch(no);
        }
        return result;
    }

    //后序查找
    public HeroNode postOrderSearch(int no) {
        HeroNode result = null;
        if (this.left != null) {
            result = this.left.postOrderSearch(no);
        }
        if (result != null) {
            return result;
        }
        if (this.right != null) {
            result = this.right.postOrderSearch(no);
        }
        if (result != null) {
            return result;
        }
        //左右子树都没有找到,就比较当前节点是不是
        if (this.no == no) {
            return this;
        }
        return result;
    }
}