6.9(Java)二叉搜索树

1.我的代码:

public class BinarySearchTree {
    class TreeNode {
        public int key;
        public TreeNode left;
        public TreeNode right;

        public TreeNode(int key) {
            this.key = key;
        }
    }
    public TreeNode root;     // 根节点

    // 插入一个元素,注意，不能插入重复的值，如果这样，插入失败
    public boolean insert(int key) {
        TreeNode newNode = new TreeNode(key);
        if (this.root == null) {
            this.root = newNode;
            return true;
        }
        TreeNode parent = null;
        TreeNode cur = this.root;
        while (cur != null) {
            if (key == cur.key) {
                return false;
            } else if (key < cur.key) {
                parent = cur;
                cur = cur.left;
            } else {
                parent = cur;
                cur = cur.right;
            }
        }
        if (key < parent.key) {
            parent.left = newNode;
        } else {
            parent.right = newNode;
        }
        return true;
    }

    // 查找key是否存在
    public TreeNode search(int key) {
        if (this.root == null) {
            return null;
        }
        TreeNode cur = this.root;
        while (cur != null) {
            if (key == cur.key) {
                return cur;
            } else if (key < cur.key) {
                cur = cur.left;
            } else {
                cur = cur.right;
            }
        }
        return null;
    }

    // 删除key的值
    public boolean removeTreeNode(int key) {
        if (this.root == null) {
            return false;
        }
        TreeNode parent = null;
        TreeNode cur = this.root;
        while (cur != null) {
            if (key == cur.key) {
                this.remove(parent, cur);
                return true;
            } else if (key < cur.key) {
                parent = cur;
                cur = cur.left;
            } else {
                parent = cur;
                cur = cur.right;
            }
        }
        return false;
    }

    private void remove(TreeNode parent, TreeNode cur) {
        // 分三种大情况
        // 1.该节点左边为空
        if (cur.left == null) {
            // 三种小情况
            if (cur == this.root) {
                this.root = cur.right;
            } else if (cur == parent.left) {
                parent.left = cur.right;
            } else { // cur == parent.right
                parent.right = cur.right;
            }
        } else if (cur.right == null) { // 2.右边为空
            // 三种小情况
            if (cur == this.root) {
                this.root = cur.left;
            } else if (cur == parent.left) {
                parent.left = cur.left;
            } else { // cur == parent.right
                parent.right = cur.left;
            }
        } else {// 3.左右都不空，使用替罪羊法，找右边最小的替代，然后删除该替代
            TreeNode tmpParent = cur;
            TreeNode tmpCur = cur.right;
            while (tmpCur.left != null) {
                tmpParent = tmpCur;
                tmpCur = tmpCur.left;
            }
            cur.key = tmpCur.key;
            // 考虑特殊情况，没有进while循环
            if (cur == tmpParent) {
                cur.right = tmpCur.right;
            } else {
                tmpParent.left = tmpCur.right;
            }
        }
    }

}

public class Test {
    public static void main(String[] args) {
        BinarySearchTree binarySearchTree = new BinarySearchTree();
        int[] array = {12, 4, 5, 10, 8, 3};
        for (int x : array) {
            binarySearchTree.insert(x);
        }
        binarySearchTree.removeTreeNode(5);
    }
}

重点研究删除问题,见以上代码.