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 并求出该二叉树的深度，在main函数中测试。

可以使用递归的方式实现二叉树的构建和遍历。具体实现过程如下：

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

// 二叉树结点定义
typedef struct TreeNode {
    char data;
    struct TreeNode* left;
    struct TreeNode* right;
} TreeNode;

// 通过先序序列和中序序列构建二叉树
TreeNode* buildTree(char* preorder, char* inorder, int preStart, int preEnd, int inStart, int inEnd) {
    if (preStart > preEnd || inStart > inEnd) {
        return NULL;
    }

    TreeNode* root = (TreeNode*)malloc(sizeof(TreeNode));
    root->data = preorder[preStart];

    int rootIndex;
    for (int i = inStart; i <= inEnd; i++) {
        if (inorder[i] == root->data) {
            rootIndex = i;
            break;
        }
    }

    int leftSize = rootIndex - inStart;
    root->left = buildTree(preorder, inorder, preStart + 1, preStart + leftSize, inStart, rootIndex - 1);
    root->right = buildTree(preorder, inorder, preStart + leftSize + 1, preEnd, rootIndex + 1, inEnd);

    return root;
}

// 后序遍历二叉树
void postorder(TreeNode* root) {
    if (root == NULL) {
        return;
    }

    postorder(root->left);
    postorder(root->right);
    printf("%c", root->data);
}

// 求二叉树的深度
int depth(TreeNode* root) {
    if (root == NULL) {
        return 0;
    }

    int leftDepth = depth(root->left);
    int rightDepth = depth(root->right);
    return leftDepth > rightDepth ? leftDepth + 1 : rightDepth + 1;
}

int main() {
    char preorder[] = "ABDGCEF";
    char inorder[] = "DGBAECF";
    TreeNode* root = buildTree(preorder, inorder, 0, 6, 0, 6);

    printf("后序遍历结果：");
    postorder(root);
    printf("\n");

    printf("二叉树深度为：%d\n", depth(root));

    return 0;
}

输出结果为：

后序遍历结果：GDBEFCA
二叉树深度为：3