Java基礎之二叉搜索樹的基本操作

/**
 * user：ypc；
 * date：2021-05-18;
 * time: 15:09;
 */
     class Node {
        int val;
        Node left;
        Node right;

        Node(int val) {
            this.val = val;
        }
    }
    public void insert(int key) {
        Node node = new Node(key);
        if (this.root == null) {
            root = node;
        }
        Node cur = root;
        Node parent = null;
        while (cur != null) {
            if (cur.val == key) {
                //System.out.println("元素已經存在");
                return;
            } else if (cur.val > key) {
                parent = cur;
                cur = cur.left;
            } else {
                parent = cur;
                cur = cur.right;
            }
        }
        if (key > parent.val) {
            parent.right = node;
        } else {
            parent.left = node;
        }

    }

 public boolean search(int key) {
        Node cur = root;
        while (cur != null) {
            if (cur.val == key) {
                return true;
            } else if (cur.val > key) {
                cur = cur.left;
            } else {
                cur = cur.right;
            }
        }

        return false;
    }

 public void removenode1(Node parent, Node cur) {
        if (cur.left == null) {
            if (cur == root) {
                root = cur.right;
            } else if (cur == parent.right) {
                parent.left = cur.right;
            } else {
                parent.right = cur.right;
            }
        } else if (cur.right == null) {
            if (cur == root) {
                root.left = cur;
            } else if (cur == parent.right) {
                parent.right = cur.left;
            } else {
                parent.left = cur.left;
            }
        } else {
            Node tp = cur;
            Node t = cur.right;
            while (t.left != null) {
                tp = t;
                t = t.left;
            }
            if (tp.left == t) {
                cur.val = t.val;
                tp.left = t.right;
            }
            if (tp.right == t) {
                cur.val = t.val;
                tp.right = t.right;
            }
        }

    }

    public void remove(int key) {
        Node cur = root;
        Node parent = null;
        while (cur != null) {
            if (cur.val == key) {
                removenode1(parent, cur);
              //removenode2(parent, cur);
                return;
            } else if (key > cur.val) {
                parent = cur;
                cur = cur.right;
            } else {
                parent = cur;
                cur = cur.left;
            }
        }
    }
  

 public void removenode2(Node parent, Node cur) {

        if (cur.left == null) {
            if (cur == root) {
                root = cur.right;
            } else if (cur == parent.right) {
                parent.left = cur.right;
            } else {
                parent.right = cur.right;
            }
        } else if (cur.right == null) {
            if (cur == root) {
                root.left = cur;
            } else if (cur == parent.right) {
                parent.right = cur.left;
            } else {
                parent.left = cur.left;
            }
        } else {
            Node tp = cur;
            Node t = cur.left;
            while (t.right != null) {
                tp = t;
                t = t.right;
            }
            if (tp.right == t) {
                cur.val = t.val;
                tp.right = t.left;
            }
            if (tp.left == t) {
                cur.val = t.val;
                tp.left = t.left;
            }
        }

    }

 /**
 * user：ypc；
 * date：2021-05-18;
 * time: 15:09;
 */
class TestBinarySearchTree {
    public static void main(String[] args) {
        int a[] = {5, 3, 4, 1, 7, 8, 2, 6, 0, 9};
        BinarySearchTree binarySearchTree = new BinarySearchTree();
        for (int i = 0; i < a.length; i++) {
            binarySearchTree.insert(a[i]);
        }
        binarySearchTree.inOrderTree(binarySearchTree.root);
        System.out.println();
        binarySearchTree.preOrderTree(binarySearchTree.root);
        binarySearchTree.remove(7);
        System.out.println();
        System.out.println("方法一刪除後");
        binarySearchTree.inOrderTree(binarySearchTree.root);
        System.out.println();
        binarySearchTree.preOrderTree(binarySearchTree.root);
    }
}