"->"令牌之前的预期非限定 ID

expected unqualified-id before ‘->’ token

本文关键字：ID gt 令牌      更新时间：2023-10-16

我正试图从数组中创建一个b树，我已经想出了这个代码，但它没有编译，并且给了我这个错误:" ' -> '令牌前预期的非限定id "，在第42行:

node->balance = right_height - left_height;

下面是完整的代码:

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cmath>
struct node {
    node *left;
    node *right;
    int balance;
    int value;
};
node *build_subtree(int *items, int length, void* node_mem, int *height = NULL) {
    /*This will give either the middle node or immediately to the right.*/
    int root_index = length / 2; 
    /* Make the node. It will be at the same index in its
       memory block as its value. Who needs memory management? */
    node *root = (node*)((char*)node_mem + sizeof(node) * root_index);
    root->value = *(items + root_index);
    /* These values will be used to compute the node balance */
    int left_height = 0, right_height = 0;
    /* Build the left subtree */
    if (root_index > 0) {
        root->left = build_subtree(items,
                                   root_index, 
                                   node_mem, 
                                   &left_height);
    }
    /* Build the right subtree */
    if (root_index < length - 1) {
        root->right = build_subtree(items, root_index,
                                    (char*)node_mem + sizeof(node) * root_index, 
                                    &right_height);
    }
    /* Compute the balance and height of the node.
       The height is 1 + the greater of the subtrees' heights. */
    node->balance = right_height - left_height;
    if (height) {
        *height = (left_height > right_height ? left_height : right_height) + 1;
    }
    return root;
}
int main() {
    int values[10000000];
    for (int i=1; i<=10000000; i++)
        values[i] = i;
    void *mem = malloc(sizeof(node) * 10000000);
    memset(mem, 0, sizeof(node) * 10000000);
    node *root = build_subtree(values, 10000000, mem);
}

Please help D:

node是一个类型，而不是指针的名称。所以node->balance在语法上是不正确的

node是一个结构体，不是指针的名称。你想用平衡，它是这个结构的一个变量。因此，您必须使用节点对象来达到变量平衡，如root: root->balance。

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