下面是给定一棵二叉树的先序遍历序列和中序遍历序列，输出后序遍历序列的c语言代码

以下是二叉树后序遍历的 C 语言代码实现：

#include <stdio.h>  
#include <stdlib.h>  
  
typedef struct Node  
{  
    char data;  
    struct Node *left;  
    struct Node *right;  
}Node, *pNode;  
  
Node *createTree(char *preorder, char *inorder, int length)  
{  
    if(preorder == NULL || inorder == NULL || length <= 0)  
        return NULL;  
  
    Node *root = (Node*)malloc(sizeof(Node));  
    root->data = *preorder;  
  
    int rootIndex = 0;  
    while(rootIndex < length && *(inorder + rootIndex) != *preorder)  
        ++rootIndex;  
  
    if(rootIndex >= length)  
        return NULL;  
  
    root->left = createTree(preorder + 1, inorder, rootIndex);  
    root->right = createTree(preorder + rootIndex + 1, inorder + rootIndex + 1, length - rootIndex - 1);  
  
    return root;  
}  
  
void postorderTraversal(Node *root)  
{  
    if(root == NULL)  
        return;  
  
    postorderTraversal(root->left);  
    postorderTraversal(root->right);  
    printf("%c ", root->data);  
}  
  
int main()  
{  
    char preorder[] = "ABDECFG";  
    char inorder[] = "DBEAFCG";  
    int length = sizeof(preorder) / sizeof(char);  
  
    Node *root = createTree(preorder, inorder, length);  
    printf("The postorder traversal of the binary tree is: ");  
    postorderTraversal(root);  
  
    return 0;  
}  

其中，createTree 函数用于根据给定的先序遍历序列和中序遍历序列构建二叉树，postorderTraversal 函数用于输出后序遍历序列。需要注意的是，以上代码中的二叉树假定没有重复的节点。