BST插入无法正常工作 [英] BST insert not working

问题描述

我正在尝试为二进制搜索树实现代码.问题是以下代码无法正常工作，但是如果我通过双指针来插入诸如insert(struct bst ** node，data)之类的funcion，它就可以工作.我认为它也应该与传递单个指针一起使用.谁能解释这里的错误是什么?

I was trying to implement a code for binary search trees. Problem is following code is not working but it works if I pass double pointer to insert funcion like insert(struct bst** node, data). I think it should also work with passing single pointers. Can anyone explain what is the error here ?

void insert(struct bst* node, int data )
{
    if (node == NULL)
    {
        printf("here with %d\n",data);
        node = (struct bst*)malloc(sizeof(struct bst));
        node->data = data;
        node->left = NULL;
        node->right = NULL;
    }
    if(data < node->data)
    {
        insert(node->left,data);
    }
    else if(data > node->data)
    {
        insert(node->right,data);
    }
}

推荐答案

如果要更改传递给函数的指针的值，则应将其作为指针传递给指针.

If you want to change the value of the pointer passed to a function, you should pass it as pointer to a pointer.

void alloc_int(int** p)
{
  *p = malloc(sizeof(int));
}

int main()
{
  int* p = NULL;
  alloc_int(&p);
  *p = 10; // here memory for p is allocated so you can use it
  free(p);
  return 0;
}

与您的示例相同.您必须传递指针的地址来更改其值(指针的值是实际数据的地址).

The same thing in your example. You have to pass an address of pointer to change its value (value of the pointer is address of actual data).

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