用C语言实现二叉树的基本操作： (1)实现二叉树的创建功能； (2)实现遍历功能，先序；打印出遍历序列； (3)实现“结点的度”的统计功能；输出每个结点的度；（4）计算树的深度。

下面是用C语言实现二叉树的基本操作的代码：

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

typedef struct node {
    int data;
    struct node *left;
    struct node *right;
} Node;

Node *createNode(int data) {
    Node *newNode = (Node*)malloc(sizeof(Node));
    newNode->data = data;
    newNode->left = NULL;
    newNode->right = NULL;
    return newNode;
}

Node *createTree() {
    int data;
    printf("Enter data (-1 for no node): ");
    scanf("%d", &data);
    if (data == -1) {
        return NULL;
    }
    Node *root = createNode(data);
    printf("Enter left child of %d:\n", data);
    root->left = createTree();
    printf("Enter right child of %d:\n", data);
    root->right = createTree();
    return root;
}

void preorder(Node *root) {
    if (root == NULL) {
        return;
    }
    printf("%d ", root->data);
    preorder(root->left);
    preorder(root->right);
}

void countDegree(Node *root) {
    if (root == NULL) {
        return;
    }
    int degree = 0;
    if (root->left != NULL) {
        degree++;
    }
    if (root->right != NULL) {
        degree++;
    }
    printf("Node %d has degree %d\n", root->data, degree);
    countDegree(root->left);
    countDegree(root->right);
}

int treeDepth(Node *root) {
    if (root == NULL) {
        return 0;
    }
    int leftDepth = treeDepth(root->left);
    int rightDepth = treeDepth(root->right);
    return (leftDepth > rightDepth) ? leftDepth + 1 : rightDepth + 1;
}

int main() {
    Node *root = createTree();
    printf("Preorder traversal: ");
    preorder(root);
    printf("\n");
    countDegree(root);
    int depth = treeDepth(root);
    printf("Tree depth: %d\n", depth);
    return 0;
}

运行示例：

Enter data (-1 for no node): 1
Enter left child of 1:
Enter data (-1 for no node): 2
Enter left child of 2:
Enter data (-1 for no node): -1
Enter right child of 2:
Enter data (-1 for no node): -1
Enter right child of 1:
Enter data (-1 for no node): 3
Enter left child of 3:
Enter data (-1 for no node): -1
Enter right child of 3:
Enter data (-1 for no node): -1
Preorder traversal: 1 2 3 
Node 1 has degree 2
Node 2 has degree 0
Node 3 has degree 0
Tree depth: 2