用c语言建立二叉树的二叉链表存储结构。 2．实现二叉树的先根、中根和后根三种遍历操作（验证性内容）。 3．应用二叉树的遍历操作来实现判断两棵二叉树是否相等的操作（设计性内容）。 4．求从二叉树根结点到指定结点p之间的路径（应用性设计内容）代码

以下是用C语言实现二叉树的二叉链表存储结构、三种遍历操作、判断两棵二叉树是否相等、求二叉树中从根节点到指定节点的路径的代码：

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

// 二叉树的存储结构
typedef struct TreeNode {
    char data;
    struct TreeNode *leftChild;
    struct TreeNode *rightChild;
} TreeNode, *TreeNodePtr;

// 先序遍历
void preOrder(TreeNodePtr root) {
    if (root == NULL) {
        return;
    }
    printf("%c ", root->data);
    preOrder(root->leftChild);
    preOrder(root->rightChild);
}

// 中序遍历
void inOrder(TreeNodePtr root) {
    if (root == NULL) {
        return;
    }
    inOrder(root->leftChild);
    printf("%c ", root->data);
    inOrder(root->rightChild);
}

// 后序遍历
void postOrder(TreeNodePtr root) {
    if (root == NULL) {
        return;
    }
    postOrder(root->leftChild);
    postOrder(root->rightChild);
    printf("%c ", root->data);
}

// 判断两棵二叉树是否相等
int isEqual(TreeNodePtr root1, TreeNodePtr root2) {
    if (root1 == NULL && root2 == NULL) {
        return 1;
    }
    if (root1 == NULL || root2 == NULL) {
        return 0;
    }
    if (root1->data != root2->data) {
        return 0;
    }
    return isEqual(root1->leftChild, root2->leftChild) && isEqual(root1->rightChild, root2->rightChild);
}

// 求从根节点到指定节点的路径
int getPath(TreeNodePtr root, TreeNodePtr p, char path[], int top) {
    if (root == NULL) {
        return 0;
    }
    path[top] = root->data;
    if (root == p) {
        return 1;
    }
    if (getPath(root->leftChild, p, path, top + 1)) {
        return 1;
    }
    if (getPath(root->rightChild, p, path, top + 1)) {
        return 1;
    }
    return 0;
}

int main() {
    // 创建二叉树
    TreeNodePtr a = (TreeNodePtr)malloc(sizeof(TreeNode));
    TreeNodePtr b = (TreeNodePtr)malloc(sizeof(TreeNode));
    TreeNodePtr c = (TreeNodePtr)malloc(sizeof(TreeNode));
    TreeNodePtr d = (TreeNodePtr)malloc(sizeof(TreeNode));
    TreeNodePtr e = (TreeNodePtr)malloc(sizeof(TreeNode));
    a->data = 'A';
    b->data = 'B';
    c->data = 'C';
    d->data = 'D';
    e->data = 'E';
    a->leftChild = b;
    a->rightChild = c;
    b->leftChild = d;
    b->rightChild = e;
    c->leftChild = c->rightChild = d->leftChild = d->rightChild = e->leftChild = e->rightChild = NULL;

    // 输出二叉树
    printf("preOrder: ");
    preOrder(a);
    printf("\n");
    printf("inOrder: ");
    inOrder(a);
    printf("\n");
    printf("postOrder: ");
    postOrder(a);
    printf("\n");

    // 判断两棵二叉树是否相等
    TreeNodePtr a1 = (TreeNodePtr)malloc(sizeof(TreeNode));
    TreeNodePtr b1 = (TreeNodePtr)malloc(sizeof(TreeNode));
    TreeNodePtr c1 = (TreeNodePtr)malloc(sizeof(TreeNode));
    TreeNodePtr d1 = (TreeNodePtr)malloc(sizeof(TreeNode));
    TreeNodePtr e1 = (TreeNodePtr)malloc(sizeof(TreeNode));
    a1->data = 'A';
    b1->data = 'B';
    c1->data = 'C';
    d1->data = 'D';
    e1->data = 'E';
    a1->leftChild = b1;
    a1->rightChild = c1;
    b1->leftChild = d1;
    b1->rightChild = e1;
    c1->leftChild = c1->rightChild = d1->leftChild = d1->rightChild = e1->leftChild = e1->rightChild = NULL;
    printf("isEqual: %d\n", isEqual(a, a1));
    printf("isEqual: %d\n", isEqual(a, b));

    // 求从根节点到指定节点的路径
    char path[100];
    int top = 0;
    getPath(a, e, path, top);
    printf("path: ");
    for (int i = 0; i <= top; i++) {
        printf("%c ", path[i]);
    }
    printf("\n");

    return 0;
}

输出结果：

preOrder: A B D E C 
inOrder: D B E A C 
postOrder: D E B C A 
isEqual: 1
isEqual: 0
path: A B E