【Java数据结构】---Map和Set(二叉搜索树)

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

public boolean insert(int key) {
    if (root == null) {
      root = new Node(key);
      return true;
   }
    Node cur = root;
     Node parent = null;
    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;
     }
   }
    Node node = new Node(key);
    if (key < parent.key) {
      parent.left = node;
   } else {
      parent.right = node;
   }
    return true;
 }

//找到根节点的位置
public void remove(int key) {
        TreeNode cur = root;
        TreeNode parent = null;
        while (cur != null) {
            if(cur.val < key) {
                parent = cur;
                cur = cur.right;
            }else if(cur.val > key) {
                parent = cur;
                cur = cur.left;
            }else {
                removeNode(parent,cur);
                return;
            }
        }
    }

    private void removeNode(TreeNode parent, TreeNode cur) {
        //左孩子不存在
        if(cur.left == null) {
            //删除节点为根节点
            if(cur == root) {
                root = cur.right;
            }else if(parent.left == cur) {//删除节点是父的左节点
                parent.left = cur.right;
            }else {////删除节点是父的右节点
                parent.right = cur.right;
            }
         //右孩子不存在
        }else if(cur.right == null) {
            if(cur == root) {
                root = cur.left;
            }else if(parent.left == cur) {
                parent.left = cur.left;
            }else {
                parent.right = cur.left;
            }
         //左右孩子均存在
         //用被删除结点的右子树的最小元素或者左子树的最大元素替代被删除结点。
        }else {
            TreeNode targetParent = cur;
            TreeNode target = cur.right;
            while (target.left != null) {
                targetParent = target;
                target = target.left;
            }
            cur.val = target.val;
            if(targetParent.left == target) {
                targetParent.left = target.right;
            }else {
                targetParent.right = target.right;
            }
        }
    }