c语言实现通过二叉树的先序序列和中序序列构建二叉树，然后在main函数中输入二叉树的先序序列为ABDGCEF，中序遍历序列为DGBAECF，并通过后序遍历算法输出二叉树的后序序列GDBEFCA

下面是具体的代码实现：

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

// 定义二叉树结构体
typedef struct TreeNode {
    char data;
    struct TreeNode *left;
    struct TreeNode *right;
} TreeNode;

// 在中序序列中查找根节点的位置
int findRoot(char *inOrder, int inStart, int inEnd, char rootVal) {
    for (int i = inStart; i <= inEnd; i++) {
        if (inOrder[i] == rootVal) {
            return i;
        }
    }
    return -1;
}

// 根据先序和中序序列构建二叉树
TreeNode* buildTree(char *preOrder, char *inOrder, int inStart, int inEnd) {
    static int preIndex = 0; // 静态变量记录先序序列的下标
    if (inStart > inEnd) {
        return NULL;
    }
    TreeNode *root = (TreeNode*)malloc(sizeof(TreeNode));
    root->data = preOrder[preIndex++];
    int rootIndex = findRoot(inOrder, inStart, inEnd, root->data); // 查找根节点在中序序列中的位置
    root->left = buildTree(preOrder, inOrder, inStart, rootIndex - 1);
    root->right = buildTree(preOrder, inOrder, rootIndex + 1, inEnd);
    return root;
}

// 后序遍历二叉树
void postOrder(TreeNode *root) {
    if (root) {
        postOrder(root->left);
        postOrder(root->right);
        printf("%c", root->data);
    }
}

int main() {
    char preOrder[] = "ABDGCEF"; // 先序序列
    char inOrder[] = "DGBAECF"; // 中序序列
    int len = sizeof(preOrder) / sizeof(preOrder[0]);
    TreeNode *root = buildTree(preOrder, inOrder, 0, len - 1);
    printf("后序遍历序列为：");
    postOrder(root);
    return 0;
}

运行结果为：

后序遍历序列为：GDBEFCA