请用c语言写一段红黑树的插入

### 回答1：

我可以为您提供一段c语言代码，用于插入红黑树：/* Function to insert a new node with given data in RB Tree */
struct node* insert(struct node* root, int data)
{
// Allocate memory for new node
struct node* newnode = (struct node*)malloc(sizeof(struct node));

// Assign data to this node
newnode->data = data;

// Initialize left and right children as NULL
newnode->left = NULL;
newnode->right = NULL;
newnode->color = 1;

// If root is NULL, return new node
if (root == NULL)
return newnode;

// Traverse the tree and find a place to insert new node
struct node* temp = root;
struct node* parent = NULL;

while (temp != NULL)
{
parent = temp;

if (data < temp->data)
temp = temp->left;
else
temp = temp->right;
}

// Make the appropriate links
if (data < parent->data)
parent->left = newnode;
else
parent->right = newnode;

// Return root of the tree
return root;
}

### 回答2：
要使用C语言写一段红黑树的插入，可以参考下面的代码。

#include <stdio.h>
#include <stdlib.h>

typedef struct Node {
    int key;
    int color; // 0为黑色，1为红色
    struct Node* left;
    struct Node* right;
    struct Node* parent;
} Node;

Node* root = NULL; // 红黑树的根节点

// 创建一个新节点
Node* createNode(int key) {
    Node* node = (Node*)malloc(sizeof(Node));
    node->key = key;
    node->color = 1; // 新插入的节点默认为红色
    node->left = NULL;
    node->right = NULL;
    node->parent = NULL;
    return node;
}

// 左旋操作
void leftRotate(Node* x) {
    Node* y = x->right;
    x->right = y->left;
    if (y->left != NULL) {
        y->left->parent = x;
    }
    y->parent = x->parent;
    if (x->parent == NULL) {
        root = y;
    } else if (x == x->parent->left) {
        x->parent->left = y;
    } else {
        x->parent->right = y;
    }
    y->left = x;
    x->parent = y;
}

// 右旋操作
void rightRotate(Node* y) {
    Node* x = y->left;
    y->left = x->right;
    if (x->right != NULL) {
        x->right->parent = y;
    }
    x->parent = y->parent;
    if (y->parent == NULL) {
        root = x;
    } else if (y == y->parent->left) {
        y->parent->left = x;
    } else {
        y->parent->right = x;
    }
    x->right = y;
    y->parent = x;
}

// 插入节点修正红黑树性质
void fixInsert(Node* node) {
    while (node != root && node->parent->color == 1) {
        if (node->parent == node->parent->parent->left) {
            Node* y = node->parent->parent->right;
            if (y != NULL && y->color == 1) {
                node->parent->color = 0;
                y->color = 0;
                node->parent->parent->color = 1;
                node = node->parent->parent;
            } else {
                if (node == node->parent->right) {
                    node = node->parent;
                    leftRotate(node);
                }
                node->parent->color = 0;
                node->parent->parent->color = 1;
                rightRotate(node->parent->parent);
            }
        } else {
            Node* y = node->parent->parent->left;
            if (y != NULL && y->color == 1) {
                node->parent->color = 0;
                y->color = 0;
                node->parent->parent->color = 1;
                node = node->parent->parent;
            } else {
                if (node == node->parent->left) {
                    node = node->parent;
                    rightRotate(node);
                }
                node->parent->color = 0;
                node->parent->parent->color = 1;
                leftRotate(node->parent->parent);
            }
        }
    }
    root->color = 0;
}

// 将节点插入红黑树
void insert(int key) {
    Node* node = createNode(key);
    Node* y = NULL;
    Node* x = root;
    while (x != NULL) {
        y = x;
        if (node->key < x->key) {
            x = x->left;
        } else {
            x = x->right;
        }
    }
    node->parent = y;
    if (y == NULL) {
        root = node;
    } else if (node->key < y->key) {
        y->left = node;
    } else {
        y->right = node;
    }
    fixInsert(node);
}

// 前序遍历红黑树
void preOrder(Node* node) {
    if (node != NULL) {
        printf("%d ", node->key);
        preOrder(node->left);
        preOrder(node->right);
    }
}

int main() {
    insert(10);
    insert(20);
    insert(30);
    insert(15);
    insert(18);

    printf("前序遍历红黑树：\n");
    preOrder(root);

    return 0;
}

上述代码实现了简单的红黑树插入功能。在插入节点后，使用`fixInsert()`函数来修正红黑树的性质，保证整棵树仍然是一颗合法的红黑树。最后，打印红黑树的前序遍历结果。