利用二叉树的扩展遍历序列生成二叉树，并将二叉树的三种遍历序列全部输出数据类型定义 ： typedef struct BTNode{ Elemtype data; struct BTNode *lchild,*rchild; }BTNode,*BTree;

好的，下面是相应的代码实现：

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

typedef char Elemtype;

typedef struct BTNode {
    Elemtype data;
    struct BTNode* lchild;
    struct BTNode* rchild;
} BTNode, *BTree;

BTree build_tree(char* str, int* index) {
    if (str[*index] == '#') {
        (*index)++;
        return NULL;
    }
    BTNode* node = (BTNode*)malloc(sizeof(BTNode));
    node->data = str[*index];
    (*index)++;
    node->lchild = build_tree(str, index);
    node->rchild = build_tree(str, index);
    return node;
}

void preorder(BTree root) {
    if (root != NULL) {
        printf("%c ", root->data);
        preorder(root->lchild);
        preorder(root->rchild);
    }
}

void inorder(BTree root) {
    if (root != NULL) {
        inorder(root->lchild);
        printf("%c ", root->data);
        inorder(root->rchild);
    }
}

void postorder(BTree root) {
    if (root != NULL) {
        postorder(root->lchild);
        postorder(root->rchild);
        printf("%c ", root->data);
    }
}

int main() {
    char str[] = "ABD##E##CF###";
    int index = 0;
    BTree root = build_tree(str, &index);
    printf("Preorder traversal: ");
    preorder(root);
    printf("\nInorder traversal: ");
    inorder(root);
    printf("\nPostorder traversal: ");
    postorder(root);
    printf("\n");
    return 0;
}

输出结果为：

Preorder traversal: A B D E C F 
Inorder traversal: D B E A F C 
Postorder traversal: D E B F C A